Organometallic Complex, Light-Emitting Element, Light-Emitting Device, Electronic Device, and Lighting Device

ABSTRACT

An object is to provide a novel organometallic complex. Another object is to provide an organometallic complex that can exhibit yellow to blue phosphorescence. A platinum complex with a tetracoordinate ligand including a phenothiazine skeleton or a phenoxazine skeleton is provided. In the ligand, nitrogen at the 10-position and carbon at the 2-position of the phenothiazine skeleton or the phenoxazine skeleton have a pyridyl group and a phenoxy group, respectively. A five-membered heteroaromatic residue is present at the 3-position of the phenoxy group. The five-membered heteroaromatic residue has two or three nitrogen atoms in its skeleton. Carbon at the 1-position of the phenothiazine skeleton or the phenoxazine skeleton and carbon at the 2-position of the phenoxy group are bonded to platinum, and nitrogen of the pyridyl group and nitrogen or carbene carbon of the five-membered heteroaromatic residue are coordinated to platinum.

This application is a divisional of copending U.S. application Ser. No.15/137,460, filed on Apr. 25, 2016 which is incorporated herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

One embodiment of the present invention relates to an organometalliccomplex, and a light-emitting element, a display module, a lightingmodule, a display device, a light-emitting device, an electronic device,and a lighting device each including the organometallic complex. Notethat one embodiment of the present invention is not limited to the abovetechnical field. The technical field of one embodiment of the inventiondisclosed in this specification and the like relates to an object, amethod, or a manufacturing method. In addition, one embodiment of thepresent invention relates to a process, a machine, manufacture, or acomposition of matter. Specifically, examples of the technical field ofone embodiment of the present invention disclosed in this specificationinclude a semiconductor device, a display device, a liquid crystaldisplay device, a light-emitting device, a lighting device, a powerstorage device, a memory device, a method for driving any of them, and amethod for manufacturing any of them.

2. Description of the Related Art

As next generation lighting devices or display devices, display devicesusing light-emitting elements (organic EL elements) in which organiccompounds or organometallic complexes are used as light-emittingsubstances have been developed and reported because of their potentialfor thinness, lightness, high-speed response to input signals, low powerconsumption, and the like.

In an organic EL element, voltage application between electrodes,between which a light-emitting layer is interposed, causes recombinationof electrons and holes injected from the electrodes, which brings alight-emitting substance into an excited state, and the return from theexcited state to the ground state is accompanied by light emission.Since the spectrum of light emitted from a light-emitting substancedepends on the light-emitting substance, use of different types oflight-emitting substances makes it possible to obtain light-emittingelements which exhibit various colors.

Although displays or lighting devices including light-emitting elementscan be suitably used for a variety of electronic devices as describedabove, their performance has plenty of room to improve. Specifically,there have not been many kinds of materials that emit green to bluephosphorescence, and further improvement of their characteristics hasbeen demanded.

Patent Document 1 discloses an iridium complex with a ligand including aphenothiazine skeleton.

REFERENCE Patent Document

[Patent Document 1] PCT International Publication No. 2004/081019

SUMMARY OF THE INVENTION

An object of one embodiment of the present invention is to provide anovel organometallic complex. Another object is to provide anorganometallic complex that can exhibit yellow to blue phosphorescence.

An object of another embodiment of the present invention is to provide anovel light-emitting element. Another object is to provide alight-emitting element with high emission efficiency. Another object isto provide a display module, a lighting module, a light-emitting device,a display device, an electronic device, and a lighting device eachhaving low power consumption.

It is only necessary that at least one of the above objects be achievedin one embodiment of the present invention. Note that the description ofthese objects does not preclude the existence of other objects. Oneembodiment of the present invention does not necessarily have all theseobjects. Other objects will be apparent from and can be derived from thedescription of the specification, the drawings, the claims, and thelike.

An organometallic complex of one embodiment of the present invention canbe represented by the following general formula (G1).

In the above general formula (G1), each of R¹ to R¹³ independentlyrepresents any of hydrogen, a substituted or unsubstituted alkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted phenylgroup, A represents a five-membered heteroaromatic skeleton includingtwo or three nitrogen atoms, and Q represents a sulfur atom or an oxygenatom.

The organometallic complex of one embodiment of the present inventioncan also be represented by the following general formula (G2).

In the above general formula (G2), each of R¹ to R¹³ independentlyrepresents any of hydrogen, a substituted or unsubstituted alkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted phenylgroup, and each of X¹, Y¹, and Z¹ independently represents a nitrogenatom or a carbon atom. Note that none or one of X¹, Y¹, and Z¹represents a nitrogen atom. In addition, Q represents a sulfur atom oran oxygen atom.

Two or three of X¹, Y¹, and Z¹ each represent a carbon atom, and thecarbon atom may have a substituent. In such a case, as the substituent,a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms ora substituted or unsubstituted phenyl group can be used.

The organometallic complex of one embodiment of the present inventioncan also be represented by the following general formula (G3).

In the above general formula (G3), each of R¹ to R¹³ and R²⁰independently represents any of hydrogen, a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms, and a substituted orunsubstituted phenyl group, and each of X² and Z² independentlyrepresents a nitrogen atom or a carbon atom. When one of X² and Z²represents a nitrogen atom, the other thereof represents a carbon atom.In addition, Q represents a sulfur atom or an oxygen atom.

When one or both of X² and Z² represent a carbon atom, the carbon atommay have a substituent. In such a case, as the substituent, asubstituted or unsubstituted alkyl group having 1 to 6 carbon atoms or asubstituted or unsubstituted phenyl group can be used.

The organometallic complex of one embodiment of the present inventioncan also be represented by the following general formula (G4).

In the above general formula (G4), each of R¹ to R¹³ and R²¹independently represents any of hydrogen, a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms, and a substituted orunsubstituted phenyl group, and each of Y³ and Z³ independentlyrepresents a nitrogen atom or a carbon atom. When one of Y³ and Z³represents a nitrogen atom, the other thereof represents a carbon atom.In addition, Q represents a sulfur atom or an oxygen atom.

When one or both of Y³ and Z³ represent a carbon atom, the carbon atommay have a substituent. In such a case, as the substituent, asubstituted or unsubstituted alkyl group having 1 to 6 carbon atoms or asubstituted or unsubstituted phenyl group can be used.

The organometallic complex of one embodiment of the present inventioncan also be represented by the following general formula (G5).

In the above general formula (G5), each of R¹ to R¹³ and R²²independently represents any of hydrogen, a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms, and a substituted orunsubstituted phenyl group, and each of X⁴ and Y⁴ independentlyrepresents a nitrogen atom or a carbon atom. When one of X⁴ and Y⁴represents a nitrogen atom, the other thereof represents a carbon atom.In addition, Q represents a sulfur atom or an oxygen atom.

When one or both of X⁴ and Y⁴ represent a carbon atom, the carbon atommay have a substituent. In such a case, as the substituent, asubstituted or unsubstituted alkyl group having 1 to 6 carbon atoms or asubstituted or unsubstituted phenyl group can be used.

The organometallic complex of one embodiment of the present inventioncan also be represented by the following general formula (G6).

In the above general formula (G6), each of R¹ to R¹³ and R³⁰ to R³²independently represents any of hydrogen, a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms, and a substituted orunsubstituted phenyl group, and Q represents a sulfur atom or an oxygenatom.

Another embodiment of the present invention is an organometallic complexwhich has the above structure and in which each of R³⁰ and R³²represents a substituted or unsubstituted alkyl group.

Another embodiment of the present invention is an organometallic complexwhich has any of the above structures and in which R³¹ represents asubstituted or unsubstituted alkyl group or a substituted orunsubstituted phenyl group.

Another embodiment of the present invention is an organometallic complexwhich has any of the above structures and in which R³ represents asubstituted or unsubstituted alkyl group or a substituted orunsubstituted phenyl group.

Another embodiment of the present invention is an organometallic complexwhich has any of the above structures and in which one or both of R³ andR³¹ represent a t-butyl group or a phenyl group.

Another embodiment of the present invention is a light-emitting elementincluding any one of the above organometallic complexes.

Another embodiment of the present invention is a light-emitting deviceincluding the above light-emitting element, and a transistor or asubstrate.

Another embodiment of the present invention is an electronic deviceincluding the above light-emitting device, and a sensor, an operationbutton, a speaker, or a microphone.

Another embodiment of the present invention is a lighting deviceincluding the above light-emitting device and a housing.

Note that the light-emitting device in this specification includes animage display device using a light-emitting element. The light-emittingdevice may be included in a module in which a light-emitting element isprovided with a connector such as an anisotropic conductive film or atape carrier package (TCP), a module in which a printed wiring board isprovided at the end of a TCP, and a module in which an integratedcircuit (IC) is directly mounted on a light-emitting element by a chipon glass (COG) method. The light-emitting device may be included inlighting equipment.

One embodiment of the present invention makes it possible to provide anovel organometallic complex. One embodiment of the present inventionmakes it possible to provide an organometallic complex exhibiting yellowto blue phosphorescence.

Another embodiment of the present invention makes it possible to providea novel light-emitting element. Another embodiment of the presentinvention makes it possible to provide a display module, a lightingmodule, a light-emitting device, a display device, an electronic device,and a lighting device each having low power consumption.

It is only necessary that at least one of the above effects be achievedin one embodiment of the present invention. Note that the description ofthese effects does not preclude the existence of other effects. Oneembodiment of the present invention does not necessarily achieve all theeffects listed above. Other effects will be apparent from and can bederived from the description of the specification, the drawings, theclaims, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are conceptual diagrams of light-emitting elements.

FIGS. 2A and 2B are conceptual diagrams of an active matrixlight-emitting device.

FIGS. 3A and 3B are conceptual diagrams of active matrix light-emittingdevices.

FIG. 4 is a conceptual diagram of an active matrix light-emittingdevice.

FIGS. 5A and 5B are conceptual diagrams of a passive matrixlight-emitting device.

FIGS. 6A and 6B illustrate a lighting device.

FIGS. 7A, 7B1, 7B2, 7C, and 7D illustrate electronic devices.

FIG. 8 illustrates a light source device.

FIG. 9 illustrates a lighting device.

FIG. 10 illustrates a lighting device.

FIG. 11 illustrates in-vehicle display devices and lighting devices.

FIGS. 12A to 12C illustrate an electronic device.

FIGS. 13A to 13C illustrate an electronic device.

FIGS. 14A and 14B show NMR charts of [Pt(pptOppz)].

FIG. 15 shows absorption and emission spectra of [Pt(pptOppz)] at roomtemperature.

FIG. 16 shows an emission spectrum of [Pt(pptOppz)] at 77 K.

FIG. 17 shows current density-luminance characteristics of alight-emitting element 1.

FIG. 18 shows luminance-current efficiency characteristics of alight-emitting element 1.

FIG. 19 shows voltage-luminance characteristics of a light-emittingelement 1.

FIG. 20 shows voltage-current characteristics of a light-emittingelement 1.

FIG. 21 shows luminance-external quantum efficiency characteristics of alight-emitting element 1.

FIG. 22 shows an emission spectrum of a light-emitting element 1.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be explained in detail belowwith reference to the drawings. Note that the present invention is notlimited to the description below, and it is easily understood by thoseskilled in the art that modes and details can be modified in variousways without departing from the spirit and scope of the presentinvention. Accordingly, the present invention should not be interpretedas being limited to the content of the embodiments below.

One embodiment of the present invention is a platinum complex with atetracoordinate ligand including a phenothiazine skeleton or aphenoxazine skeleton. In the ligand, nitrogen at the 10-position andcarbon at the 2-position of the phenothiazine skeleton or thephenoxazine skeleton have a pyridyl group and a phenoxy group,respectively. A five-membered heteroaromatic residue is present at the3-position of the phenoxy group. The five-membered heteroaromaticresidue has two or three nitrogen atoms in its skeleton. In addition,carbon at the 1-position of the phenothiazine skeleton or thephenoxazine skeleton and carbon at the 2-position of the phenoxy groupare bonded to platinum, and nitrogen of the pyridyl group and nitrogenor carbene carbon of the five-membered heteroaromatic residue arecoordinated to platinum.

An organometallic complex having such a structure is a novelorganometallic complex and can emit yellow to blue phosphorescence.

The organometallic complex can also be represented by the followinggeneral formula (G1).

In the above general formula (G1), each of R¹ to R¹³ independentlyrepresents any of hydrogen, a substituted or unsubstituted alkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted phenylgroup, A represents a five-membered heteroaromatic skeleton includingtwo or three nitrogen atoms, and Q represents a sulfur atom or an oxygenatom.

Specific examples of the five-membered heteroaromatic skeleton includingtwo or three nitrogen atoms are a pyrazolyl group, an imidazolyl group,a 1,2,3-triazolyl group, a 1,2,4-triazolyl group, a nitrogen-containingheterocyclic carbene skeleton (e.g., an imidazolium skeleton, abenzimidazolium skeleton, and a triazolium skeleton), and the like.

The organometallic complex of one embodiment of the present inventioncan also be represented by the following general formula (G2).

In the above general formula (G2), each of R¹ to R¹³ independentlyrepresents any of hydrogen, a substituted or unsubstituted alkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted phenylgroup, and each of X¹, Y¹, and Z¹ independently represents a nitrogenatom or a carbon atom. Note that none or one of X¹, Y¹, and Z¹represents a nitrogen atom. In addition, Q represents a sulfur atom oran oxygen atom.

Two or three of X¹, Y¹, and Z¹ each represent a carbon atom, and thecarbon atom may have a substituent or no substituent. In the case wherethe carbon atom has a substituent, as the substituent, a substituted orunsubstituted alkyl group having 1 to 6 carbon atoms or a substituted orunsubstituted phenyl group can be used.

The organometallic complex of one embodiment of the present inventioncan also be represented by the following general formula (G3).

In the above general formula (G3), each of R¹ to R¹³ and R²⁰independently represents any of hydrogen, a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms, and a substituted orunsubstituted phenyl group, and each of X² and Z² independentlyrepresents a nitrogen atom or a carbon atom. When one of X² and Z²represents a nitrogen atom, the other thereof represents a carbon atom.In addition, Q represents a sulfur atom or an oxygen atom.

When one or both of X² and Z² represent a carbon atom, the carbon atommay have a substituent or no substituent. In the case where the carbonatom has a substituent, as the substituent, a substituted orunsubstituted alkyl group having 1 to 6 carbon atoms or a substituted orunsubstituted phenyl group can be used.

The organometallic complex of one embodiment of the present inventioncan also be represented by the following general formula (G4).

In the above general formula (G4), each of R¹ to R¹³ and R²¹independently represents any of hydrogen, a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms, and a substituted orunsubstituted phenyl group, and each of Y³ and Z³ independentlyrepresents a nitrogen atom or a carbon atom. When one of Y³ and Z³represents a nitrogen atom, the other thereof represents a carbon atom.In addition, Q represents a sulfur atom or an oxygen atom.

When one or both of Y³ and Z³ represent a carbon atom, the carbon atommay have a substituent or no substituent. In the case where the carbonatom has a substituent, as the substituent, a substituted orunsubstituted alkyl group having 1 to 6 carbon atoms or a substituted orunsubstituted phenyl group can be used.

The organometallic complex of one embodiment of the present inventioncan also be represented by the following general formula (G5).

In the above general formula (G5), each of R¹ to R¹³ and R²²independently represents any of hydrogen, a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms, and a substituted orunsubstituted phenyl group, and each of X⁴ and Y⁴ independentlyrepresents a nitrogen atom or a carbon atom. When one of X⁴ and Y⁴represents a nitrogen atom, the other thereof represents a carbon atom.When one or both of X⁴ and Y⁴ represent a carbon atom, the carbon atommay have a substituent or no substituent. In addition, Q represents asulfur atom or an oxygen atom.

The organometallic complex represented by the above general formula (G5)can also be represented by the following general formulae (G5-1) and(G5-2).

In the above general formulae (G5-1) and (G5-2), each of R¹ to R¹³independently represents any of hydrogen, a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms, and a substituted orunsubstituted phenyl group, and each of X⁴, Y⁴, and Z⁴ independentlyrepresents a nitrogen atom or a carbon atom. Note that one or two of X⁴,Y⁴, and Z⁴ represent a nitrogen atom. In the case where one or two ofX⁴, Y⁴, and Z⁴ represent a carbon atom, the carbon atom may have asubstituent or no substituent. In addition, Q represents a sulfur atomor an oxygen atom.

The organometallic complex of one embodiment of the present inventioncan also be represented by the following general formula (G6).

In the above general formula (G6), each of R¹ to R¹³ and R³⁰ to R³²independently represents any of hydrogen, a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms, and a substituted orunsubstituted phenyl group, and Q represents a sulfur atom or an oxygenatom.

In the organometallic complex having the above structure, each of R³⁰and R³² preferably represents a substituted or unsubstituted alkylgroup. Each of R³⁰ and R³² preferably represents a methyl group, inwhich case the thermophysical properties and stability of the materialare improved.

In the organometallic complex having the above structure, the nitrogenatom of the pyridyl group bonded to nitrogen at the 10-position of thephenothiazine skeleton or the phenoxazine skeleton is coordinated toplatinum, which is a central metal. A bulky substituent is preferablypresent at carbon on the para-position with respect to the nitrogenatom, in which case the thermophysical properties and stability of thematerial are improved and characteristics for narrowing an emissionspectrum and increasing emission efficiency are obtained. Thus, in theorganometallic complex represented by the above general formula, R³ ispreferably a substituted or unsubstituted alkyl group or a substitutedor unsubstituted phenyl group, particularly preferably a substituted orunsubstituted t-butyl group or a substituted or unsubstituted phenylgroup.

In the organometallic complex having the above structure, R³¹ ispreferably a bulky substituent, in which case the thermophysicalproperties and stability of the material are improved andcharacteristics for narrowing an emission spectrum and increasingemission efficiency are obtained. Thus, in the organometallic complexrepresented by the above general formula (G6), R³¹ is preferably asubstituted or unsubstituted alkyl group or a substituted orunsubstituted phenyl group, particularly preferably a substituted orunsubstituted t-butyl group or a substituted or unsubstituted phenylgroup.

Note that in the case where the expression “a substituted orunsubstituted alkyl group having 1 to 6 carbon atoms” is used or in thecase where an alkyl group having 1 to 6 carbon atoms “may have asubstituent” in this specification, a halogeno group, an alkoxy grouphaving 1 to 6 carbon atoms, or the like can be used as a substituentthat may be bonded to the alkyl group. Similarly, in the case where theexpression “a substituted or unsubstituted phenyl group” is used or inthe case where a phenyl group “may have a substituent,” an alkyl grouphaving 1 to 6 carbon atoms, a halogeno group, an alkoxy group having 1to 6 carbon atoms, or the like can be used as a substituent that may bebonded to the phenyl group.

Specific examples of an alkyl group having 1 to 6 carbon atoms include amethyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group,an n-pentyl group, a 1-methylbutyl group, a 2-methylbutyl group, a3-methylbutyl group, a 1-ethylpropyl group, a 1,1-dimethylpropyl group,a 1,2-dimethylpropyl group, a 2,2-dimethylpropyl group, and a branchedor non-branched hexyl group. In addition, examples of a halogeno groupinclude a fluoro group, a chloro group, a bromo group, and an iodogroup. In addition, examples of an alkoxy group having 1 to 6 carbonatoms include a straight-chain or branched-chain alkyloxy group such asa methoxy group, an ethoxy group, a propoxy group, an isopropoxy group,a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxygroup, and a hexyloxy group, and an alkenyloxy group such as a vinyloxygroup, a propenyloxy group, a butenyloxy group, a pentenyloxy group, anda hexenyloxy group.

Specific examples of a substituted or unsubstituted phenyl group are aphenyl group, a 2-methylphenyl group, a 2,5-dimethylphenyl group, a2,6-dimethylphenyl group, a 2,6-diethylphenyl group, a2,6-diisopropylphenyl group, a 2,6-diisobutylphenyl group, a2,6-dicyclopropylphenyl group, a 2,4,6-trimethylphenyl group, a4-fluorophenyl group, a 2,6-difluorophenyl group, a4-trifluoromethylphenyl group, a 4-cyanophenyl group, a 4-methoxyphenylgroup, a 3,4-dimethoxyphenyl group, a 3,4-methylenedioxyphenyl group, a4-trifluoromethoxyphenyl group, a 4-dimethylaminophenyl group, and thelike.

Some specific examples of the organometallic complexes of embodiments ofthe present invention with the above-described structures are shownbelow.

An example of a method of synthesizing the above-describedorganometallic complex of one embodiment of the present invention isdescribed.

<Method of Synthesizing Phenothiazine Derivative or PhenoxazineDerivative>

First, an example of a method of synthesizing a phenothiazine derivativeor a phenoxazine derivative represented by a general formula (G0) belowis described. In the general formula (G0), each of R¹ to R¹³independently represents any of hydrogen, a substituted or unsubstitutedalkyl group having 1 to 6 carbon atoms, and a substituted orunsubstituted phenyl group, A represents a five-membered heteroaromaticskeleton including two or three nitrogen atoms, and Q represents sulfuror oxygen.

As illustrated in a scheme below, a hydroxy compound (A1) and a halide(A2) are reacted, whereby the phenothiazine derivative or thephenoxazine derivative can be obtained. In the scheme below, Xrepresents a halogen, each of R¹ to R¹³ independently represents any ofhydrogen, a substituted or unsubstituted alkyl group having 1 to 6carbon atoms, and a substituted or unsubstituted phenyl group, and Arepresents a five-membered heteroaromatic skeleton including two orthree nitrogen atoms. Note that the method of synthesizing thephenothiazine derivative or the phenoxazine derivative is not limited tothe scheme below. For example, (A1) may be an alkoxide compound insteadof the hydroxy compound, or alternatively, (A1) may be a halide and (A2)may be a hydroxy compound.

In the above manner, the phenothiazine derivative or the phenoxazinederivative can be synthesized under a very simple synthesis scheme.

<<Method of Synthesizing Organometallic Complex which is One Embodimentof the Present Invention and Represented by General Formula (G1)>>

First, as illustrated in a synthesis scheme below, a mixed solution ofthe phenothiazine derivative or the phenoxazine derivative representedby the general formula (G0), potassium tetrachloroplatinate, and aceticacid or a solvent containing acetic acid is heated in an inert gasatmosphere, whereby the organometallic complex which is one embodimentof the present invention and represented by the general formula (G1) canbe obtained.

In the synthesis scheme above, each of R¹ to R¹³ independentlyrepresents any of hydrogen, a substituted or unsubstituted alkyl grouphaving 1 to 6 carbon atoms, and a substituted or unsubstituted phenylgroup, and A represents a five-membered heteroaromatic skeletonincluding two or three nitrogen atoms.

<<Light-Emitting Element>>

Next, an example of a light-emitting element which is one embodiment ofthe present invention is described in detail below with reference toFIG. 1A.

In this embodiment, the light-emitting element includes a pair ofelectrodes (a first electrode 101 and a second electrode 102), and an ELlayer 103 provided between the first electrode 101 and the secondelectrode 102. Note that the first electrode 101 functions as an anodeand the second electrode 102 functions as a cathode.

To function as an anode, the first electrode 101 is preferably formedusing any of metals, alloys, conductive compounds having a high workfunction (specifically, a work function of 4.0 eV or more), mixturesthereof, and the like. Specific examples include indium oxide-tin oxide(ITO: indium tin oxide), indium oxide-tin oxide containing silicon orsilicon oxide, indium oxide-zinc oxide, and indium oxide containingtungsten oxide and zinc oxide (IWZO). Films of such conductive metaloxides are usually formed by a sputtering method, but may be formed byapplication of a sol-gel method or the like. In an example of theformation method, indium oxide-zinc oxide is deposited by a sputteringmethod using a target obtained by adding 1 wt % to 20 wt % of zinc oxideto indium oxide. Furthermore, a film of indium oxide containing tungstenoxide and zinc oxide (IWZO) can be formed by a sputtering method using atarget in which tungsten oxide and zinc oxide are added to indium oxideat 0.5 wt % to 5 wt % and 0.1 wt % to 1 wt %, respectively. Otherexamples are gold (Au), platinum (Pt), nickel (Ni), tungsten (W),chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu),palladium (Pd), nitrides of metal materials (e.g., titanium nitride),and the like. Graphene can also be used. Note that when a compositematerial described later is used for a layer which is in contact withthe first electrode 101 in the EL layer 103, an electrode material canbe selected regardless of its work function.

It is preferable that the EL layer 103 have a stacked-layer structureand any of the layers of the stacked-layer structure contain theorganometallic complex represented by any one of the general formulae(G1) to (G6) above.

The stacked-layer structure of the EL layer 103 can be formed bycombining a hole-injection layer, a hole-transport layer, alight-emitting layer, an electron-transport layer, an electron-injectionlayer, a carrier-blocking layer, an intermediate layer, and the like asappropriate. In this embodiment, the EL layer 103 has a structure inwhich a hole-injection layer 111, a hole-transport layer 112, alight-emitting layer 113, an electron-transport layer 114, and anelectron-injection layer 115 are stacked in this order over the firstelectrode 101. Specific examples of the materials forming the layers aregiven below.

The hole-injection layer 111 is a layer that contains a substance with ahigh hole-injection property. Molybdenum oxide, vanadium oxide,ruthenium oxide, tungsten oxide, manganese oxide, or the like can beused. Alternatively, the hole-injection layer 111 can be formed using aphthalocyanine-based compound such as phthalocyanine (abbreviation:H₂Pc) or copper phthalocyanine (abbreviation: CuPc), an aromatic aminecompound such as4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB) orN,N′-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine(abbreviation: DNTPD), a high molecular compound such aspoly(3,4-ethylenedioxythiophene)/poly(styrenesulfonic acid) (PEDOT/PSS),or the like.

Alternatively, a composite material in which a substance with ahole-transport property contains a substance with an acceptor propertycan be used for the hole-injection layer 111. Note that the use of sucha substance with a hole-transport property which contains a substancewith an acceptor property enables selection of a material used to forman electrode regardless of its work function. In other words, besides amaterial having a high work function, a material having a low workfunction can be used for the first electrode 101. As examples of thesubstance having an acceptor property,7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F₄-TCNQ), chloranil, and the like can be given. In addition, transitionmetal oxides can be given. Moreover, oxides of metals belonging toGroups 4 to 8 of the periodic table can be given. Specifically, it ispreferable to use vanadium oxide, niobium oxide, tantalum oxide,chromium oxide, molybdenum oxide, tungsten oxide, manganese oxide, andrhenium oxide because of their high electron accepting properties. Inparticular, molybdenum oxide is more preferable because of its stabilityin the atmosphere, low hygroscopic property, and easiness of handling.

As the substance with a hole-transport property which is used for thecomposite material, any of a variety of organic compounds such asaromatic amine compounds, carbazole derivatives, aromatic hydrocarbons,and high molecular compounds (e.g., oligomers, dendrimers, or polymers)can be used. Note that the substance with a hole-transport propertywhich is used for the composite material is preferably a substancehaving a hole mobility of 10⁻⁶ cm²/Vs or more. Organic compounds thatcan be used as the substance with a hole-transport property in thecomposite material are specifically given below.

Examples of the aromatic amine compounds that can be used for thecomposite material are N,N′-di(p-tolyl)-N,N′-diphenyl-p-phenylenediamine(abbreviation: DTDPPA),4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl (abbreviation:DPAB),N,N′-bis{4-[bis(3-methylphenyl)amino]phenyl}-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine(abbreviation: DNTPD),1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene(abbreviation: DPA3B), and the like. Specific examples of the carbazolederivatives are3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1), 4,4′-di(N-carbazolyl)biphenyl (abbreviation:CBP), 1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB),9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation: CzPA),1,4-bis[4-(N-carbazolyl)phenyl]-2,3,5,6-tetraphenylbenzene, and thelike. Examples of the aromatic hydrocarbons are2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),2-tert-butyl-9,10-di(1-naphthyl)anthracene,9,10-bis(3,5-diphenylphenyl)anthracene (abbreviation: DPPA),2-tert-butyl-9,10-bis(4-phenylphenyl)anthracene (abbreviation: t-BuDBA),9,10-di(2-naphthyl)anthracene (abbreviation: DNA),9,10-diphenylanthracene (abbreviation: DPAnth), 2-tert-butylanthracene(abbreviation: t-BuAnth), 9,10-bis(4-methyl-1-naphthyl)anthracene(abbreviation: DMNA), 2-tert-butyl-9,10-bis[2-(1-naphthyl)phenyl]anthracene, 9,10-bis[2-(1-naphthyl)phenyl]anthracene,2,3,6,7-tetramethyl-9,10-di(1-naphthyl)anthracene,2,3,6,7-tetramethyl-9,10-di(2-naphthyl)anthracene, 9,9′-bianthryl,10,10′-diphenyl-9,9′-bianthryl,10,10′-bis(2-phenylphenyl)-9,9′-bianthryl,10,10′-bis[(2,3,4,5,6-pentaphenyl)phenyl]-9,9′-bianthryl, anthracene,tetracene, rubrene, perylene, 2,5,8,11-tetra(tert-butyl)perylene, andthe like. Besides, pentacene, coronene, or the like can also be used.The aromatic hydrocarbons may have a vinyl skeleton. Examples of thearomatic hydrocarbon having a vinyl skeleton are4,4′-bis(2,2-diphenylvinyl)biphenyl (abbreviation: DPVBi),9,10-bis[4-(2,2-diphenylvinyl)phenyl] anthracene (abbreviation: DPVPA),and the like.

A high molecular compound such as poly(N-vinylcarbazole) (abbreviation:PVK), poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine](abbreviation:poly-TPD) can also be used.

By providing the hole-injection layer, a high hole-injection propertycan be achieved to allow a light-emitting element to be driven at a lowvoltage.

Note that the hole-injection layer may be formed of the above-describedacceptor material alone or of the above-described acceptor material andanother material in combination. In this case, the acceptor materialextracts electrons from the hole-transport layer, so that holes can beinjected into the hole-transport layer. The acceptor material transfersthe extracted electrons to the anode.

The hole-transport layer 112 is a layer that contains a substance with ahole-transport property. Examples of the substance with a hole-transportproperty are aromatic amine compounds such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine(abbreviation: TDATA),4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: MTDATA),4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: BPAFLP), and the like. The substances mentioned here havehigh hole-transport properties and are mainly ones that have a holemobility of 10⁻⁶ cm²/Vs or more. An organic compound given as an exampleof the substance with a hole-transport property in the compositematerial described above can also be used for the hole-transport layer112. A high molecular compound such as poly(N-vinylcarbazole)(abbreviation: PVK) or poly(4-vinyltriphenylamine) (abbreviation: PVTPA)can also be used. Note that the layer that contains a substance with ahole-transport property is not limited to a single layer, and may be astack of two or more layers including any of the above substances.

The light-emitting layer 113 may be a layer that emits fluorescence, alayer that emits phosphorescence, or a layer emitting thermallyactivated delayed fluorescence (TADF). Furthermore, the light-emittinglayer 113 may be a single layer or include a plurality of layerscontaining different light-emitting substances. In the case where thelight-emitting layer including a plurality of layers is formed, a layercontaining a phosphorescent substance and a layer containing afluorescent substance may be stacked. In that case, an exciplexdescribed later is preferably utilized for the layer containing thephosphorescent substance.

As the fluorescent substance, any of the following substances can beused, for example. Fluorescent substances other than those given belowcan also be used. Examples of the fluorescent substance are5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2′-bipyridine (abbreviation:PAP2BPy), 5,6-bis[4′-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2′-bipyridine(abbreviation: PAPP2BPy),N,N-diphenyl-N,N-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6FLPAPrn),N,N-bis(3-methylphenyl)-N,N-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPrn),N,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA), perylene, 2,5,8,11-tetra(tert-butyl)perylene(abbreviation: TBP),4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA),N,N″-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N′-triphenyl-1,4-phenylenediamine](abbreviation: DPABPA),N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: 2PCAPPA),N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPPA),N,N,N′,N′,N″N″,N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine(abbreviation: DBC1), coumarin 30,N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCABPhA),N-(9,10-diphenyl-2-anthryl)-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPA),N-[9,10-bis(1,1′-biphenyl-2-yl)-2-anthryl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPABPhA),9,10-bis(1,1′-biphenyl-2-yl)-N-[4-(9H-carbazol-9-yl)phenyl]-N-phenylanthracen-2-amine(abbreviation: 2YGABPhA), N,N,9-triphenylanthracen-9-amine(abbreviation: DPhAPhA), coumarin 545T, N,N′-diphenylquinacridone(abbreviation: DPQd), rubrene,5,12-bis(1,1′-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT),2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile(abbreviation: DCMI),2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCM2),N,N,N′,N′-tetrakis(4-methylphenyl)tetracene-5,11-diamine (abbreviation:p-mPhTD),7,14-diphenyl-N,N,N′,N-tetrakis(4-methylphenyl)acenaphtho[1,2-a]fluoranthene-3,10-diamine(abbreviation: p-mPhAFD),2-{2-isopropyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTI),2-{2-tert-butyl-6-[2-(1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: DCJTB),2-(2,6-bis{2-[4-(dimethylamino)phenyl]ethenyl}-4H-pyran-4-ylidene)propanedinitrile(abbreviation: BisDCM),2-{2,6-bis[2-(8-methoxy-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile(abbreviation: BisDCJTM), and the like. Condensed aromatic diaminecompounds typified by pyrenediamine compounds such as 1,6FLPAPrn and1,6mMemFLPAPrn are preferable because of their high hole-trappingproperties, high emission efficiency, and high reliability.

Examples of a material which can be used as a phosphorescent substancein the light-emitting layer 113 are as follows. The examples includeorganometallic iridium complexes having 4H-triazole skeletons, such astris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN²]phenyl-κC}iridium(III)(abbreviation: [Ir(mpptz-dmp)₃]),tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Mptz)₃]), andtris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(iPrptz-3b)₃]); organometallic iridium complexeshaving 1H-triazole skeletons, such astris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(Mptz1-mp)₃]) andtris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Prptz1-Me)₃]); organometallic iridium complexeshaving imidazole skeletons, such asfac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole]iridium(III)(abbreviation: [Ir(iPrpmi)₃]) andtris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III)(abbreviation: [Ir(dmpimpt-Me)₃]); and organometallic iridium complexesin which a phenylpyridine derivative having an electron-withdrawinggroup is a ligand, such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C²′]iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: FIr6),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C²′]iridium(III) picolinate(abbreviation: FIrpic),bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C²′}iridium(III)picolinate (abbreviation: [Ir(CF₃ppy)₂(pic)]), andbis[2-(4′,6′-difluorophenyl)pyridinato-N,C²′]iridium(III)acetylacetonate (abbreviation: FIr(acac)). These are compounds emittingblue phosphorescence and have an emission peak at 440 nm to 520 nm.

Other examples include organometallic iridium complexes havingpyrimidine skeletons, such astris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation:[Ir(mppm)₃]), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₃]),(acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₂(acac)]),(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]),(acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(nbppm)₂(acac)]),(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III) (abbreviation: [Ir(mpmppm)₂(acac)]), and(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: [Ir(dppm)₂(acac)]); organometallic iridium complexeshaving pyrazine skeletons, such as(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-Me)₂(acac)]) and(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-iPr)₂(acac)]); organometallic iridium complexeshaving pyridine skeletons, such astris(2-phenylpyridinato-N,C²′)iridium(III) (abbreviation: [Ir(ppy)₃]),bis(2-phenylpyridinato-N,C²′)iridium(III) acetylacetonate (abbreviation:[Ir(ppy)₂(acac)]), bis(benzo[h]quinolinato)iridium(III) acetylacetonate(abbreviation: [Ir(bzq)₂(acac)]), tris(benzo[h]quinolinato)iridium(III)(abbreviation: [Ir(bzq)₃]), tris(2-phenylquinolinato-N,C²′)iridium(III)(abbreviation: [Ir(pq)₃]), andbis(2-phenylquinolinato-N,C²′)iridium(III) acetylacetonate(abbreviation: [Ir(pq)₂(acac)]); and rare earth metal complexes such astris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation:[Tb(acac)₃(Phen)]). These are mainly compounds emitting greenphosphorescence and have an emission peak at 500 nm to 600 nm. Note thatorganometallic iridium complexes having pyrimidine skeletons havedistinctively high reliability and emission efficiency and thus areespecially preferable.

Other examples include organometallic iridium complexes havingpyrimidine skeletons, such as(diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III) (abbreviation: [Ir(5mdppm)₂(dibm)]),bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: [Ir(5mdppm)₂(dpm)]), andbis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: [Ir(dlnpm)₂(dpm)]); organometallic iridium complexeshaving pyrazine skeletons, such as(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]),bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III)(abbreviation: [Ir(tppr)₂(dpm)]), and(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: [Ir(Fdpq)₂(acac)]); organometallic iridium complexeshaving pyridine skeletons, such astris(1-phenylisoquinolinato-N,C²′)iridium(III) (abbreviation:[Ir(piq)₃]) and bis(1-phenylisoquinolinato-N,C²′)iridium(III)acetylacetonate (abbreviation: [Ir(piq)₂(acac)]); platinum complexessuch as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II)(abbreviation: PtOEP); and rare earth metal complexes such astris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III)(abbreviation: [Eu(DBM)₃(Phen)]) andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: [Eu(TTA)₃(Phen)]). These are compounds emitting redphosphorescence and have an emission peak at 600 nm to 700 nm.Furthermore, organometallic iridium complexes having pyrazine skeletonscan provide red light emission with favorable chromaticity.

As well as the above phosphorescent compounds, a variety ofphosphorescent substances may be selected and used.

Note that the organometallic complex of one embodiment of the presentinvention is preferably used as the phosphorescent substance. Theorganometallic complex of one embodiment of the present invention emitslight efficiently, resulting in high emission efficiency of alight-emitting element.

Examples of the TADF material include a fullerene, a derivative thereof,an acridine derivative such as proflavine, and eosin. Furthermore, ametal-containing porphyrin, such as a porphyrin containing magnesium(Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium (In), orpalladium (Pd) can be used. Examples of the metal-containing porphyrininclude a protoporphyrin-tin fluoride complex (SnF₂(Proto IX)), amesoporphyrin-tin fluoride complex (SnF₂(Meso IX)), ahematoporphyrin-tin fluoride complex (SnF₂(Hemato IX)), a coproporphyrintetramethyl ester-tin fluoride complex (SnF₂(Copro III-4Me)), anoctaethylporphyrin-tin fluoride complex (SnF₂(OEP)), anetioporphyrin-tin fluoride complex (SnF₂(Etio I)), and anoctaethylporphyrin-platinum chloride complex (PtCl₂(OEP)), which areshown in the following structural formulae.

Alternatively, a heterocyclic compound having a n-electron richheteroaromatic ring and a π-electron deficient heteroaromatic ring, suchas2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine(abbreviation: PIC-TRZ) shown in the following structural formula, canbe used. The heterocyclic compound is preferably used because of theπ-electron rich heteroaromatic ring and the π-electron deficientheteroaromatic ring, for which the electron-transport property and thehole-transport property are high. Note that a substance in which theπ-electron rich heteroaromatic ring is directly bonded to the π-electrondeficient heteroaromatic ring is particularly preferably used becausethe donor property of the π-electron rich heteroaromatic ring and theacceptor property of the π-electron deficient heteroaromatic ring areboth high and the energy difference between the S₁ level and the T₁level becomes small.

As a host material of the light-emitting layer, variouscarrier-transport materials, such as a material with anelectron-transport property or a material with a hole-transportproperty, can be used.

Examples of the material with an electron-transport property are a metalcomplex such as bis(10-hydroxybenzo[h]quinolinato)beryllium(II)(abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq),bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), orbis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ); aheterocyclic compound having a polyazole skeleton such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation:CO11), 2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), or2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II); a heterocyclic compound having a diazineskeleton such as 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[3′-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mCzBPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine(abbreviation: 4,6mPnP2Pm), or4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation:4,6mDBTP2Pm-II); and a heterocyclic compound having a pyridine skeletonsuch as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine (abbreviation:35DCzPPy) or 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation:TmPyPB). Among the above materials, a heterocyclic compound having adiazine skeleton and a heterocyclic compound having a pyridine skeletonhave high reliability and are thus preferable. Specifically, aheterocyclic compound having a diazine (pyrimidine or pyrazine) skeletonhas a high electron-transport property to contribute to a reduction indrive voltage.

Examples of the material with a hole-transport property include acompound having an aromatic amine skeleton such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD),4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino] biphenyl(abbreviation: BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine(abbreviation: mBPAFLP),4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBA BP), 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBBi1BP),4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBANB),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine (abbreviation: PCBAF), orN-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9′-bifluoren-2-amine (abbreviation: PCBASF); a compound having acarbazole skeleton such as 1,3-bis(N-carbazolyl)benzene (abbreviation:mCP), 4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), or3,3′-bis(9-phenyl-9H-carbazole) (abbreviation: PCCP); a compound havinga thiophene skeleton such as4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation:DBT3P-II),2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene(abbreviation: DBTFLP-III), or4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene(abbreviation: DBTFLP-IV); and a compound having a furan skeleton suchas 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation:DBF3P-II) or4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran(abbreviation: mmDBFFLBi-II). Among the above materials, a compoundhaving an aromatic amine skeleton and a compound having a carbazoleskeleton are preferable because these compounds are highly reliable andhave high hole-transport properties to contribute to a reduction indrive voltage. Hole-transport materials can be selected from a varietyof substances as well as from the hole-transport materials given above.

In the case of using a fluorescent substance as a light-emittingsubstance, materials that can be suitably used are materials having ananthracene skeleton such as9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:PCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole (abbreviation:PCPN), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation:CzPA), 7-[4-(1 0-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA),6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan(abbreviation: 2mBnfPPA), and9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl}anthracene(abbreviation: FLPPA). The use of a substance having an anthraceneskeleton as the host material for the fluorescent substance makes itpossible to obtain a light-emitting layer with high emission efficiencyand high durability. In particular, CzPA, cgDBCzPA, 2mBnfPPA, and PCzPAare preferable because of their excellent characteristics.

Note that the host material may be a mixture of a plurality of kinds ofsubstances, and in the case of using a mixed host material, it ispreferable to mix a material having an electron-transport property witha material having a hole-transport property. By mixing the materialhaving an electron-transport property with the material having ahole-transport property, the transport property of the light-emittinglayer 113 can be easily adjusted and a recombination region can beeasily controlled. The ratio of the content of the material having ahole-transport property to the content of the material having anelectron-transport property may be 1:9 to 9:1.

These mixed host materials may form an exciplex. When a combination ofthese materials is selected so as to form an exciplex that exhibitslight emission whose wavelength overlaps the wavelength of alowest-energy-side absorption band of the fluorescent substance, thephosphorescent substance, or the TADF material, energy is transferredsmoothly and light emission can be obtained efficiently. Such astructure is preferable in that drive voltage can be reduced.

The light-emitting layer 113 having the above-described structure can beformed by co-evaporation by a vacuum evaporation method, or a gravureprinting method, an offset printing method, an inkjet method, a spincoating method, a dip coating method, or the like using a solution ofthe materials.

The electron-transport layer 114 contains a substance with anelectron-transport property. As the substance with an electron-transportproperty, the materials having an electron-transport property or havingan anthracene skeleton, which are described above as materials for thehost material, can be used.

Between the electron-transport layer and the light-emitting layer, alayer that controls transport of electron carriers may be provided. Thisis a layer formed by addition of a small amount of a substance having ahigh electron-trapping property to the aforementioned material having ahigh electron-transport property, and the layer is capable of adjustingcarrier balance by retarding transport of electron carriers. Such astructure is very effective in preventing a problem (such as a reductionin element lifetime) caused when electrons pass through thelight-emitting layer.

In addition, the electron-injection layer 115 may be provided in contactwith the second electrode 102 between the electron-transport layer 114and the second electrode 102. For the electron-injection layer 115, analkali metal, an alkaline earth metal, or a compound thereof, such aslithium fluoride (LiF), cesium fluoride (CsF), or calcium fluoride(CaF₂), can be used. For example, a layer that is formed using asubstance having an electron-transport property and contains an alkalimetal, an alkaline earth metal, or a compound thereof can be used. Inaddition, an electride may be used for the electron-injection layer 115.Examples of the electride include a substance in which electrons areadded at high concentration to calcium oxide-aluminum oxide. Note that alayer that is formed using a substance having an electron-transportproperty and contains an alkali metal or an alkaline earth metal ispreferably used as the electron-injection layer 115, in which caseelectron injection from the second electrode 102 is efficientlyperformed.

Instead of the electron-injection layer 115, a charge-generation layer116 may be provided (FIG. 1B). The charge-generation layer 116 refers toa layer capable of injecting holes into a layer in contact with thecathode side of the charge-generation layer 116 and electrons into alayer in contact with the anode side thereof when a potential isapplied. The charge-generation layer 116 includes at least a p-typelayer 117. The p-type layer 117 is preferably formed using any of thecomposite materials given above as examples of materials that can beused for the hole-injection layer 111. The p-type layer 117 may beformed by stacking a film containing the above-described acceptormaterial as a material included in the composite material and a filmcontaining the above-described hole-transport material. When a potentialis applied to the p-type layer 117, electrons are injected into theelectron-transport layer 114 and holes are injected into the secondelectrode 102 serving as a cathode; thus, the light-emitting elementoperates. When a layer containing the organic compound of one embodimentof the present invention exists in the electron-transport layer 114 soas to be in contact with the charge-generation layer 116, a luminancedecrease due to accumulation of driving time of the light-emittingelement can be suppressed, and thus, the light-emitting element can havea long lifetime.

Note that the charge-generation layer 116 preferably includes either anelectron-relay layer 118 or an electron-injection buffer layer 119 orboth in addition to the p-type layer 117.

The electron-relay layer 118 contains at least the substance with anelectron-transport property and has a function of preventing aninteraction between the electron-injection buffer layer 119 and thep-type layer 117 and smoothly transferring electrons. The LUMO level ofthe substance with an electron-transport property contained in theelectron-relay layer 118 is preferably between the LUMO level of anacceptor substance in the p-type layer 117 and the LUMO level of asubstance contained in a layer of the electron-transport layer 114 incontact with the charge-generation layer 116. As a specific value of theenergy level, the LUMO level of the substance with an electron-transportproperty contained in the electron-relay layer 118 is preferably higherthan or equal to −5.0 eV, more preferably higher than or equal to −5.0eV and lower than or equal to −3.0 eV. Note that as the substance withan electron-transport property in the electron-relay layer 118, aphthalocyanine-based material or a metal complex having a metal-oxygenbond and an aromatic ligand is preferably used.

A substance having a high electron-injection property can be used forthe electron-injection buffer layer 119. For example, an alkali metal,an alkaline earth metal, a rare earth metal, or a compound thereof(e.g., an alkali metal compound (including an oxide such as lithiumoxide, a halide, and a carbonate such as lithium carbonate or cesiumcarbonate), an alkaline earth metal compound (including an oxide, ahalide, and a carbonate), or a rare earth metal compound (including anoxide, a halide, and a carbonate)) can be used.

In the case where the electron-injection buffer layer 119 contains thesubstance having an electron-transport property and a donor substance,an organic compound such as tetrathianaphthacene (abbreviation: TTN),nickelocene, or decamethylnickelocene can be used as the donorsubstance, as well as an alkali metal, an alkaline earth metal, a rareearth metal, a compound of the above metal (e.g., an alkali metalcompound (including an oxide such as lithium oxide, a halide, and acarbonate such as lithium carbonate or cesium carbonate), an alkalineearth metal compound (including an oxide, a halide, and a carbonate),and a rare earth metal compound (including an oxide, a halide, and acarbonate)). Note that as the substance having an electron-transportproperty, a material similar to the above-described material used forthe electron-transport layer 114 can be used. Furthermore, the organiccompound of the present invention can be used.

For the second electrode 102, any of metals, alloys, electricallyconductive compounds, and mixtures thereof which have a low workfunction (specifically, a work function of 3.8 eV or less) or the likecan be used. Specific examples of such a cathode material are elementsbelonging to Groups 1 and 2 of the periodic table, such as alkali metals(e.g., lithium (Li) and cesium (Cs)), magnesium (Mg), calcium (Ca), andstrontium (Sr), alloys thereof (e.g., MgAg and AILi), rare earth metalssuch as europium (Eu) and ytterbium (Yb), alloys thereof, and the like.However, when the electron-injection layer is provided between thesecond electrode 102 and the electron-transport layer, for the secondelectrode 102, any of a variety of conductive materials such as Al, Ag,ITO, or indium oxide-tin oxide containing silicon or silicon oxide canbe used regardless of the work function. Films of these conductivematerials can be formed by a dry method such as a vacuum evaporationmethod or a sputtering method, an inkjet method, a spin coating method,or the like. In addition, the films of these conductive materials may beformed by a wet method using a sol-gel method, or by a wet method usingpaste of a metal material.

Any of a variety of methods can be used to form the EL layer 103regardless of whether it is a dry process or a wet process. For example,a vacuum evaporation method, a gravure printing method, an offsetprinting method, a screen printing method, an inkjet method, a spincoating method, or the like may be used.

In addition, the electrode may be formed by a wet method using a sol-gelmethod, or by a wet method using paste of a metal material.Alternatively, the electrode may be formed by a dry method such as asputtering method or a vacuum evaporation method.

Light emission from the light-emitting element is extracted out throughone or both of the first electrode 101 and the second electrode 102.Therefore, one or both of the first electrode 101 and the secondelectrode 102 are formed as a light-transmitting electrode.

The structure of the layers provided between the first electrode 101 andthe second electrode 102 is not limited to the above-describedstructure. Preferably, a light-emitting region where holes and electronsrecombine is positioned away from the first electrode 101 and the secondelectrode 102 so that quenching due to the proximity of thelight-emitting region and a metal used for electrodes andcarrier-injection layers can be prevented.

Furthermore, in order that transfer of energy from an exciton generatedin the light-emitting layer can be suppressed, preferably, thehole-transport layer and the electron-transport layer which are incontact with the light-emitting layer 113, particularly acarrier-transport layer in contact with a side closer to therecombination region in the light-emitting layer 113, are formed using asubstance having a wider band gap than the light-emitting substance ofthe light-emitting layer or the emission center substance included inthe light-emitting layer.

Next, a mode of a light-emitting element with a structure in which aplurality of light-emitting units are stacked (this type oflight-emitting element is also referred to as a stacked element) isdescribed with reference to FIG. 1C. This light-emitting elementincludes a plurality of light-emitting units between an anode and acathode. One light-emitting unit has the same structure as the EL layer103 illustrated in FIG. 1A. In other words, the light-emitting elementillustrated in FIG. 1A or 1B includes a single light-emitting unit, andthe light-emitting element illustrated in FIG. 1C includes a pluralityof light-emitting units.

In FIG. 1C, a first light-emitting unit 511 and a second light-emittingunit 512 are stacked between a first electrode 501 and a secondelectrode 502, and a charge-generation layer 513 is provided between thefirst light-emitting unit 511 and the second light-emitting unit 512.The first electrode 501 and the second electrode 502 correspond,respectively, to the first electrode 101 and the second electrode 102illustrated in FIG. 1A, and the materials given in the description forFIG. 1A can be used. Furthermore, the first light-emitting unit 511 andthe second light-emitting unit 512 may have the same structure ordifferent structures.

The charge-generation layer 513 has a function of injecting electronsinto one of the light-emitting units and injecting holes into the otherof the light-emitting units when a voltage is applied between the firstelectrode 501 and the second electrode 502. That is, in FIG. 1C, thecharge-generation layer 513 injects electrons into the firstlight-emitting unit 511 and holes into the second light-emitting unit512 when a voltage is applied so that the potential of the firstelectrode becomes higher than the potential of the second electrode.

The charge-generation layer 513 preferably has a structure similar tothe structure of the charge-generation layer 116 described withreference to FIG. 1B. Since the composite material of an organiccompound and a metal oxide is superior in carrier-injection property andcarrier-transport property, low-voltage driving or low-current drivingcan be achieved. Note that when a surface of a light-emitting unit onthe anode side is in contact with the charge-generation layer 513, thecharge-generation layer 513 can also serve as a hole-injection layer ofthe light-emitting unit; thus, a hole-transport layer is not necessarilyformed in the light-emitting unit.

In the case where the electron-injection buffer layer 119 is provided,the electron-injection buffer layer serves as the electron-injectionlayer in the light-emitting unit on the anode side and thelight-emitting unit does not necessarily further need anelectron-injection layer.

Note that when a layer in contact with a surface of thecharge-generation layer 513 on the anode side in a light-emitting unit(typically, the electron-transport layer in the light-emitting unit onthe anode side) contains the organic compound of one embodiment of thepresent invention which is described in Embodiment, a luminance decreasedue to accumulation of driving time can be suppressed, and thus, thelight-emitting element can have high reliability.

The light-emitting element having two light-emitting units is describedwith reference to FIG. 1C; however, the present invention can besimilarly applied to a light-emitting element in which three or morelight-emitting units are stacked. With a plurality of light-emittingunits partitioned by the charge-generation layer 513 between a pair ofelectrodes as in the light-emitting element according to thisembodiment, it is possible to provide an element which can emit lightwith high luminance with the current density kept low and has a longlifetime. A light-emitting device that can be driven at a low voltageand has low power consumption can be realized.

Furthermore, when emission colors of the light-emitting units are madedifferent, light emission of a desired color can be obtained from thelight-emitting element as a whole. For example, it is easy to enable alight-emitting element having two light-emitting units to emit whitelight as the whole element when the emission colors of the firstlight-emitting unit are red and green and the emission color of thesecond light-emitting unit is blue.

<<Micro Optical Resonator (Microcavity) Structure>>

A light-emitting element with a microcavity structure is formed with theuse of a reflective electrode and a semi-transmissive andsemi-reflective electrode as the pair of electrodes. The reflectiveelectrode and the semi-transmissive and semi-reflective electrodecorrespond to the first electrode and the second electrode describedabove. The light-emitting element with a microcavity structure includesat least an EL layer between the reflective electrode and thesemi-transmissive and semi-reflective electrode. The EL layer includesat least a light-emitting layer serving as a light-emitting region.

Light emitted from the light-emitting layer included in the EL layer isreflected and resonated by the reflective electrode and thesemi-transmissive and semi-reflective electrode. Note that thereflective electrode is formed using a conductive material havingreflectivity and has a visible light reflectivity of 40% to 100%,preferably 70% to 100% and a resistivity of 1×10⁻² Ωcm or lower. Inaddition, the semi-transmissive and semi-reflective electrode is formedusing a conductive material having reflectivity and a light-transmittingproperty and has a visible light reflectivity of 20% to 80%, preferably40% to 70%, and a resistivity of 1×10⁻² Ωcm or lower.

In the light-emitting element, by changing thicknesses of thetransparent conductive film, the composite material, thecarrier-transport material, and the like, the optical path lengthbetween the reflective electrode and the semi-transmissive andsemi-reflective electrode can be changed. Thus, light with a wavelengththat is resonated between the reflective electrode and thesemi-transmissive and semi-reflective electrode can be intensified whilelight with a wavelength that is not resonated therebetween can beattenuated.

Note that light that is emitted from the light-emitting layer andreflected back by the reflective electrode (first reflected light)considerably interferes with light that directly enters thesemi-transmissive and semi-reflective electrode from the light-emittinglayer (first incident light). For this reason, the optical path lengthbetween the reflective electrode and the light-emitting layer ispreferably adjusted to (2n−1)λ/4 (n is a natural number of 1 or largerand λ is a wavelength of color to be amplified). In that case, thephases of the first reflected light and the first incident light can bealigned with each other and the light emitted from the light-emittinglayer can be further amplified.

Note that in the above structure, the EL layer may be formed oflight-emitting layers or may be a single light-emitting layer. Thetandem light-emitting element described above may be combined with theEL layers; for example, a light-emitting element may have a structure inwhich a plurality of EL layers is provided, a charge-generation layer isprovided between the EL layers, and each EL layer is formed oflight-emitting layers or a single light-emitting layer.

<<Light-Emitting Device>>

A light-emitting device of one embodiment of the present invention isdescribed using FIGS. 2A and 2B. Note that FIG. 2A is a top viewillustrating the light-emitting device and FIG. 2B is a cross-sectionalview of FIG. 2A taken along lines A-B and C-D. This light-emittingdevice includes a driver circuit portion (source line driver circuit)601, a pixel portion 602, and a driver circuit portion (gate line drivercircuit) 603, which can control light emission of a light-emittingelement and illustrated with dotted lines. A reference numeral 604denotes a sealing substrate; 605, a sealing material; and 607, a spacesurrounded by the sealing material 605.

Reference numeral 608 denotes a wiring for transmitting signals to beinput to the source line driver circuit 601 and the gate line drivercircuit 603 and receiving signals such as a video signal, a clocksignal, a start signal, and a reset signal from a flexible printedcircuit (FPC) 609 serving as an external input terminal. Although onlythe FPC is illustrated here, a printed wiring board (PWB) may beattached to the FPC. The light-emitting device in the presentspecification includes, in its category, not only the light-emittingdevice itself but also the light-emitting device provided with the FPCor the PWB.

Next, a cross-sectional structure will be described with reference toFIG. 2B. The driver circuit portion and the pixel portion are formedover an element substrate 610; the source line driver circuit 601, whichis a driver circuit portion, and one of the pixels in the pixel portion602 are illustrated here.

As the source line driver circuit 601, a CMOS circuit in which ann-channel FET 623 and a p-channel FET 624 are combined is formed. Inaddition, the driver circuit may be formed with any of a variety ofcircuits such as a CMOS circuit, a PMOS circuit, or an NMOS circuit.Although a driver integrated type in which the driver circuit is formedover the substrate is described in this embodiment, the driver circuitis not necessarily formed over the substrate, and the driver circuit canbe formed outside, not over the substrate.

The pixel portion 602 includes a plurality of pixels including aswitching FET 611, a current controlling FET 612, and a first electrode613 electrically connected to a drain of the current controlling FET612. One embodiment of the present invention is not limited to thestructure. The pixel portion may include three or more FETs and acapacitor in combination.

The kind and crystallinity of a semiconductor used for the FETs is notparticularly limited; an amorphous semiconductor or a crystallinesemiconductor may be used. Examples of the semiconductor used for theFETs include Group 13 semiconductors, Group 14 semiconductors, compoundsemiconductors, oxide semiconductors, and organic semiconductormaterials. Oxide semiconductors are particularly preferable. Examples ofthe oxide semiconductor include an In—Ga oxide and an In-M-Zn oxide (Mis Al, Ga, Y, Zr, La, Ce, or Nd). Note that an oxide semiconductormaterial that has an energy gap of 2 eV or more, preferably 2.5 eV ormore, further preferably 3 eV or more is preferably used, in which casethe off-state current of the transistors can be reduced.

Note that to cover an end portion of the first electrode 613, aninsulator 614 is formed. The insulator 614 can be formed using apositive photosensitive acrylic resin film here.

The insulator 614 is formed to have a curved surface with curvature atits upper or lower end portion in order to obtain favorable coverage.For example, in the case where positive photosensitive acrylic is usedfor a material of the insulator 614, only the upper end portion of theinsulator 614 preferably has a curved surface with a curvature radius(0.2 μm to 3 μm). As the insulator 614, either a negative photosensitiveresin or a positive photosensitive resin can be used.

An EL layer 616 and a second electrode 617 are formed over the firstelectrode 613. The first electrode 613, the EL layer 616, and the secondelectrode 617 correspond, respectively, to the first electrode 101, theEL layer 103, and the second electrode 102 in FIG. 1A or 1B.

The EL layer 616 preferably contains the organometallic complex of oneembodiment of the present invention. The organometallic complex ispreferably used as an emission center substance in the light-emittinglayer.

The sealing substrate 604 is attached to the element substrate 610 withthe sealing material 605, so that a light-emitting element 618 isprovided in the space 607 surrounded by the element substrate 610, thesealing substrate 604, and the sealing material 605. The space 607 isfilled with a filler, and may be filled with an inert gas (such asnitrogen or argon) or the sealing material 605. It is preferable thatthe sealing substrate 604 be provided with a recessed portion and adrying agent be provided in the recessed portion, in which casedeterioration due to influence of moisture can be suppressed.

An epoxy-based resin or glass frit is preferably used for the sealingmaterial 605. It is preferable that such a material do not transmitmoisture or oxygen as much as possible. As the element substrate 610 andthe sealing substrate 604, a glass substrate, a quartz substrate, or aplastic substrate formed of fiber reinforced plastic (FRP), polyvinylfluoride (PVF), polyester, or acrylic can be used.

Note that in this specification and the like, a transistor or alight-emitting element can be formed using any of a variety ofsubstrates, for example. The type of a substrate is not limited to acertain type. As the substrate, a semiconductor substrate (e.g., asingle crystal substrate or a silicon substrate), an SOI substrate, aglass substrate, a quartz substrate, a plastic substrate, a metalsubstrate, a stainless steel substrate, a substrate including stainlesssteel foil, a tungsten substrate, a substrate including tungsten foil, aflexible substrate, an attachment film, paper including a fibrousmaterial, a base material film, or the like can be used, for example. Asan example of a glass substrate, a barium borosilicate glass substrate,an aluminoborosilicate glass substrate, a soda lime glass substrate, orthe like can be given. Examples of the flexible substrate, theattachment film, the base material film, and the like are substrates ofplastics typified by polyethylene terephthalate (PET), polyethylenenaphthalate (PEN), and polyether sulfone (PES). Another example is asynthetic resin such as acrylic. Alternatively, polytetrafluoroethylene(PTFE), polypropylene, polyester, polyvinyl fluoride, polyvinylchloride, or the like can be used. Alternatively, polyamide, polyimide,aramid, epoxy, an inorganic vapor deposition film, paper, or the likecan be used. Specifically, the use of semiconductor substrates, singlecrystal substrates, SOI substrates, or the like enables the manufactureof small-sized transistors with a small variation in characteristics,size, shape, or the like and with high current capability. A circuitusing such transistors achieves lower power consumption of the circuitor higher integration of the circuit.

Alternatively, a flexible substrate may be used as the substrate, andthe transistor or the light-emitting element may be provided directly onthe flexible substrate. Still alternatively, a separation layer may beprovided between the substrate and the transistor or the substrate andthe light-emitting element. The separation layer can be used when partor the whole of a semiconductor device formed over the separation layeris separated from the substrate and transferred onto another substrate.In such a case, the transistor can be transferred to a substrate havinglow heat resistance or a flexible substrate. For the separation layer, astack including inorganic films, which are a tungsten film and a siliconoxide film, or an organic resin film of polyimide or the like formedover a substrate can be used, for example.

In other words, a transistor or a light-emitting element may be formedusing one substrate, and then transferred to another substrate. Examplesof a substrate to which a transistor or a light-emitting element istransferred include, in addition to the above-described substrates overwhich transistors can be formed, a paper substrate, a cellophanesubstrate, an aramid film substrate, a polyimide film substrate, a stonesubstrate, a wood substrate, a cloth substrate (including a naturalfiber (e.g., silk, cotton, or hemp), a synthetic fiber (e.g., nylon,polyurethane, or polyester), a regenerated fiber (e.g., acetate, cupra,rayon, or regenerated polyester), or the like), a leather substrate, anda rubber substrate. When such a substrate is used, a transistor withexcellent characteristics or a transistor with low power consumption canbe formed, a device with high durability or high heat resistance can beprovided, or reduction in weight or thickness can be achieved.

FIGS. 3A and 3B each illustrate an example of a light-emitting device inwhich full color display is achieved by formation of a light-emittingelement exhibiting white light emission and with the use of coloringlayers (color filters) and the like. In FIG. 3A, a substrate 1001, abase insulating film 1002, a gate insulating film 1003, gate electrodes1006, 1007, and 1008, a first interlayer insulating film 1020, a secondinterlayer insulating film 1021, a peripheral portion 1042, a pixelportion 1040, a driver circuit portion 1041, first electrodes 1024W,1024R, 1024G, and 1024B of light-emitting elements, a partition 1025, anEL layer 1028, a second electrode 1029 of the light-emitting elements, asealing substrate 1031, a sealing material 1032, and the like areillustrated.

In FIG. 3A, coloring layers (a red coloring layer 1034R, a greencoloring layer 1034G, and a blue coloring layer 1034B) are provided on atransparent base material 1033. A black layer (a black matrix) 1035 maybe additionally provided. The transparent base material 1033 providedwith the coloring layers and the black layer is positioned and fixed tothe substrate 1001. Note that the coloring layers and the black layerare covered with an overcoat layer 1036. In FIG. 3A, light emitted frompart of the light-emitting layer does not pass through the coloringlayers, while light emitted from the other part of the light-emittinglayer passes through the coloring layers. Since light which does notpass through the coloring layers is white and light which passes throughany one of the coloring layers is red, blue, or green, an image can bedisplayed using pixels of the four colors.

Note that a light-emitting element including the organometallic complexof one embodiment of the present invention as a light-emitting substancecan have high emission efficiency and low power consumption.

FIG. 3B illustrates an example in which the coloring layers (the redcoloring layer 1034R, the green coloring layer 1034G, and the bluecoloring layer 1034B) are provided between the gate insulating film 1003and the first interlayer insulating film 1020. As in the structure, thecoloring layers may be provided between the substrate 1001 and thesealing substrate 1031.

The above-described light-emitting device is a light-emitting devicehaving a structure in which light is extracted from the substrate 1001side where the FETs are formed (a bottom emission structure), but may bea light-emitting device having a structure in which light is extractedfrom the sealing substrate 1031 side (a top emission structure). FIG. 4is a cross-sectional view of a light-emitting device having a topemission structure. In this case, a substrate which does not transmitlight can be used as the substrate 1001. The process up to the step offorming a connection electrode which connects the FET and the anode ofthe light-emitting element is performed in a manner similar to that ofthe light-emitting device having a bottom emission structure. Then, athird interlayer insulating film 1037 is formed to cover an electrode1022. This insulating film may have a planarization function. The thirdinterlayer insulating film 1037 can be formed using a material similarto that of the second interlayer insulating film, and can alternativelybe formed using any of other various materials.

The first electrodes 1024W, 1024R, 1024G, and 1024B of thelight-emitting elements each serve as an anode here, but may serve as acathode. Furthermore, in the case of a light-emitting device having atop emission structure as illustrated in FIG. 4, the first electrodesare preferably reflective electrodes. The EL layer 1028 is formed tohave a structure similar to the structure of the EL layer 103 in FIG. 1Aor 1B, with which white light emission can be obtained.

In the case of a top emission structure as illustrated in FIG. 4,sealing can be performed with the sealing substrate 1031 on which thecoloring layers (the red coloring layer 1034R, the green coloring layer1034G, and the blue coloring layer 1034B) are provided. The sealingsubstrate 1031 may be provided with the black layer (black matrix) 1035which is positioned between pixels. The coloring layers (the redcoloring layer 1034R, the green coloring layer 1034G, and the bluecoloring layer 1034B) and the black layer (the black matrix) may becovered with the overcoat layer. Note that a light-transmittingsubstrate is used as the sealing substrate 1031.

Although an example in which full color display is performed using fourcolors of red, green, blue, and white is shown here, there is noparticular limitation and full color display using three colors of red,green, and blue or four colors of red, green, blue, and yellow may beperformed.

FIGS. 5A and 5B illustrate a passive matrix light-emitting device whichis one embodiment of the present invention. FIG. 5A is a perspectiveview of the light-emitting device, and FIG. 5B is a cross-sectional viewof FIG. 5A taken along line X-Y. In FIGS. 5A and 5B, an EL layer 955 isprovided between an electrode 952 and an electrode 956 over a substrate951. An end portion of the electrode 952 is covered with an insulatinglayer 953. A partition layer 954 is provided over the insulating layer953. The sidewalls of the partition layer 954 are aslope such that thedistance between both sidewalls is gradually narrowed toward the surfaceof the substrate. In other words, a cross section taken along thedirection of the short side of the partition layer 954 is trapezoidal,and the lower side (a side which is in the same direction as a planedirection of the insulating layer 953 and in contact with the insulatinglayer 953) is shorter than the upper side (a side which is in the samedirection as the plane direction of the insulating layer 953 and not incontact with the insulating layer 953). The partition layer 954 thusprovided can prevent defects in the light-emitting element due to staticelectricity or the like.

Since many minute light-emitting elements arranged in a matrix can eachbe controlled with the FETs formed in the pixel portion, theabove-described light-emitting device can be suitably used as a displaydevice for displaying images.

<<Lighting Device>>

A lighting device which is one embodiment of the present invention isdescribed with reference to FIGS. 6A and 6B. FIG. 6B is a top view ofthe lighting device, and FIG. 6A is a cross-sectional view of FIG. 6Btaken along line e-f.

In the lighting device, a first electrode 401 is formed over a substrate400 which is a support and has a light-transmitting property. The firstelectrode 401 corresponds to the first electrode 101 in FIGS. 1A and 1B.When light is extracted through the first electrode 401 side, the firstelectrode 401 is formed using a material having a light-transmittingproperty.

A pad 412 for applying a voltage to a second electrode 404 is providedover the substrate 400.

An EL layer 403 is formed over the first electrode 401. The EL layer 403corresponds to, for example, the EL layer 103 in FIG. 1A or 1B. Refer tothe descriptions for the structure.

The second electrode 404 is formed to cover the EL layer 403. The secondelectrode 404 corresponds to the second electrode 102 in FIG. 1A. Thesecond electrode 404 contains a material having high reflectivity whenlight is extracted through the first electrode 401 side. The secondelectrode 404 is connected to the pad 412, whereby a voltage is applied.

A light-emitting element is formed with the first electrode 401, the ELlayer 403, and the second electrode 404. The light-emitting element isfixed to a sealing substrate 407 with sealing materials 405 and 406 andsealing is performed, whereby the lighting device is completed. It ispossible to use only either the sealing material 405 or the sealingmaterial 406. In addition, the inner sealing material 406 (not shown inFIG. 6B) can be mixed with a desiccant, whereby moisture is adsorbed andthe reliability is increased.

When parts of the pad 412 and the first electrode 401 are extended tothe outside of the sealing materials 405 and 406, the extended parts canserve as external input terminals. An IC chip 420 mounted with aconverter or the like may be provided over the external input terminals.

<<Electronic Device>>

Examples of an electronic device which is one embodiment of the presentinvention are described. Examples of the electronic device aretelevision devices (also referred to as TV or television receivers),monitors for computers and the like, cameras such as digital cameras anddigital video cameras, digital photo frames, mobile phones (alsoreferred to as cell phones or mobile phone devices), portable gamemachines, portable information terminals, audio playback devices, andlarge game machines such as pachinko machines. Specific examples ofthese electronic devices are given below.

FIG. 7A illustrates an example of a television device. In the televisiondevice, a display portion 7103 is incorporated in a housing 7101. Inaddition, here, the housing 7101 is supported by a stand 7105. Imagescan be displayed on the display portion 7103, and in the display portion7103, light-emitting elements are arranged in a matrix.

The television device can be operated with an operation switch of thehousing 7101 or a separate remote controller 7110. With operation keys7109 of the remote controller 7110, channels and volume can becontrolled and images displayed on the display portion 7103 can becontrolled. Furthermore, the remote controller 7110 may be provided witha display portion 7107 for displaying data output from the remotecontroller 7110.

Note that the television device is provided with a receiver, a modem,and the like. With the use of the receiver, general televisionbroadcasting can be received. Moreover, when the television device isconnected to a communication network with or without wires via themodem, one-way (from a sender to a receiver) or two-way (between asender and a receiver or between receivers) information communicationcan be performed.

FIG. 7B1 illustrates a computer, which includes a main body 7201, ahousing 7202, a display portion 7203, a keyboard 7204, an externalconnection port 7205, a pointing device 7206, and the like. Note thatthis computer is manufactured by using light-emitting elements arrangedin a matrix in the display portion 7203. The computer illustrated inFIG. 7B1 may have a structure illustrated in FIG. 7B2. A computerillustrated in FIG. 7B2 is provided with a second display portion 7210instead of the keyboard 7204 and the pointing device 7206. The seconddisplay portion 7210 is a touchscreen, and input can be performed byoperation of display for input on the second display portion 7210 with afinger or a dedicated pen. The second display portion 7210 can alsodisplay images other than the display for input. The display portion7203 may also be a touchscreen. Connecting the two screens with a hingecan prevent troubles; for example, the screens can be prevented frombeing cracked or broken while the computer is being stored or carried.

FIGS. 7C and 7D illustrate an example of a portable informationterminal. The portable information terminal is provided with a displayportion 7402 incorporated in a housing 7401, operation buttons 7403, anexternal connection port 7404, a speaker 7405, a microphone 7406, andthe like. Note that the portable information terminal has the displayportion 7402 including light-emitting elements arranged in a matrix.

Information can be input to the portable information terminalillustrated in FIGS. 7C and 7D by touching the display portion 7402 witha finger or the like. In this case, operations such as making a call andcreating an e-mail can be performed by touching the display portion 7402with a finger or the like.

There are mainly three screen modes of the display portion 7402. Thefirst mode is a display mode mainly for displaying an image. The secondmode is an input mode mainly for inputting information such ascharacters. The third mode is a display-and-input mode in which twomodes of the display mode and the input mode are combined.

For example, in the case of making a call or creating an e-mail, a textinput mode mainly for inputting text is selected for the display portion7402 so that text displayed on a screen can be input. In this case, itis preferable to display a keyboard or number buttons on almost theentire screen of the display portion 7402.

When a detection device including a sensor such as a gyroscope or anacceleration sensor for sensing inclination is provided inside themobile phone, screen display of the display portion 7402 can beautomatically changed by determining the orientation of the mobile phone(whether the mobile phone is placed horizontally or vertically).

The screen modes are switched by touch on the display portion 7402 oroperation with the operation buttons 7403 of the housing 7401. Thescreen modes can be switched depending on the kind of images displayedon the display portion 7402. For example, when a signal of an imagedisplayed on the display portion is a signal of moving image data, thescreen mode is switched to the display mode. When the signal is a signalof text data, the screen mode is switched to the input mode.

Moreover, in the input mode, when input by touching the display portion7402 is not performed for a certain period while a signal detected by anoptical sensor in the display portion 7402 is detected, the screen modemay be controlled so as to be switched from the input mode to thedisplay mode.

The display portion 7402 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken by thedisplay portion 7402 while in touch with the palm or the finger, wherebypersonal authentication can be performed. Furthermore, by providing abacklight or a sensing light source which emits near-infrared light inthe display portion, an image of a finger vein, a palm vein, or the likecan be taken.

Note that in the above electronic devices, any of the structuresdescribed in this specification can be combined as appropriate.

The display portion preferably includes a light-emitting elementincluding the organometallic complex of one embodiment of the presentinvention. The light-emitting element can have high emission efficiency.Furthermore, the light-emitting element can be driven at low voltage.Thus, the electronic device including the organometallic complex of oneembodiment of the present invention can have low power consumption.

FIG. 8 illustrates an example of a liquid crystal display deviceincluding the light-emitting element for a backlight. The liquid crystaldisplay device illustrated in FIG. 8 includes a housing 901, a liquidcrystal layer 902, a backlight unit 903, and a housing 904. The liquidcrystal layer 902 is connected to a driver IC 905. The light-emittingelement is used for the backlight unit 903, to which current is suppliedthrough a terminal 906.

As the light-emitting element, a light-emitting element including theorganometallic complex of one embodiment of the present invention ispreferably used. By including the light-emitting element, the backlightof the liquid crystal display device can have low power consumption.

FIG. 9 illustrates an example of a desk lamp which is one embodiment ofthe present invention. The desk lamp illustrated in FIG. 9 includes ahousing 2001 and a light source 2002, and a lighting device including alight-emitting element is used as the light source 2002.

FIG. 10 illustrates an example of an indoor lighting device 3001. Alight-emitting element including the organometallic complex of oneembodiment of the present invention is preferably used in the lightingdevice 3001.

An automobile which is one embodiment of the present invention isillustrated in FIG. 11. In the automobile, light-emitting elements areused for a windshield and a dashboard. Display regions 5000 to 5005 areprovided by using the light-emitting elements. The light-emittingelements preferably include the organometallic complex of one embodimentof the present invention, in which case the light-emitting elements canhave low power consumption. This also suppresses power consumption ofthe display regions 5000 to 5005, showing suitability for use in anautomobile.

The display regions 5000 and 5001 are display devices which are providedin the automobile windshield and which include the light-emittingelements. When a first electrode and a second electrode are formed ofelectrodes having light-transmitting properties in these light-emittingelements, what is called a see-through display device, through which theopposite side can be seen, can be obtained. Such a see-through displaydevice can be provided even in the automobile windshield, withouthindering the vision. Note that in the case where a transistor fordriving or the like is provided, a transistor having alight-transmitting property, such as an organic transistor using anorganic semiconductor material or a transistor using an oxidesemiconductor, is preferably used.

The display region 5002 is a display device which is provided in apillar portion and which includes the light-emitting element. Thedisplay region 5002 can compensate for the view hindered by the pillarportion by showing an image taken by an imaging unit provided in the carbody. Similarly, a display region 5003 provided in the dashboard cancompensate for the view hindered by the car body by showing an imagetaken by an imaging unit provided in the outside of the car body, whichleads to elimination of blind areas and enhancement of safety. Showingan image so as to compensate for the area which a driver cannot seemakes it possible for the driver to confirm safety easily andcomfortably.

The display region 5004 and the display region 5005 can provide avariety of kinds of information such as navigation information, aspeedometer, a tachometer, a mileage, a fuel meter, a gearshiftindicator, and air-condition setting. The content or layout of thedisplay can be changed freely by a user as appropriate. Note that suchinformation can also be shown by the display regions 5000 to 5003. Thedisplay regions 5000 to 5005 can also be used as lighting devices.

FIGS. 12A and 12B illustrate an example of a foldable tablet terminal.FIG. 12A illustrates the tablet terminal which is unfolded. The tabletterminal includes a housing 9630, a display portion 9631 a, a displayportion 9631 b, a display mode switch 9034, a power switch 9035, apower-saving mode switch 9036, a clip 9033, and an operation switch9038. Note that in the tablet terminal, one or both of the displayportion 9631 a and the display portion 9631 b is/are formed using alight-emitting device which includes the light-emitting elementcontaining the organometallic complex of one embodiment of the presentinvention.

Part of the display portion 9631 a can be a touchscreen region 9632 aand data can be input when a displayed operation key 9637 is touched.Although half of the display portion 9631 a has only a display functionand the other half has a touchscreen function, one embodiment of thepresent invention is not limited to the structure. The whole displayportion 9631 a may have a touchscreen function. For example, a keyboardcan be displayed on the entire region of the display portion 9631 a sothat the display portion 9631 a is used as a touchscreen, and thedisplay portion 9631 b can be used as a display screen.

Like the display portion 9631 a, part of the display portion 9631 b canbe a touchscreen region 9632 b. When a switching button 9639 forshowing/hiding a keyboard on the touchscreen is touched with a finger, astylus, or the like, the keyboard can be displayed on the displayportion 9631 b.

Touch input can be performed in the touchscreen region 9632 a and thetouchscreen region 9632 b at the same time.

The display mode switch 9034 can switch the display between portraitmode, landscape mode, and the like, and between monochrome display andcolor display, for example. The power-saving mode switch 9036 cancontrol display luminance in accordance with the amount of externallight in use of the tablet terminal sensed by an optical sensorincorporated in the tablet terminal. Another sensing device including asensor such as a gyroscope or an acceleration sensor for sensinginclination may be incorporated in the tablet terminal, in addition tothe optical sensor.

Although FIG. 12A illustrates an example in which the display portion9631 a and the display portion 9631 b have the same display area, oneembodiment of the present invention is not limited to the example. Thedisplay portion 9631 a and the display portion 9631 b may have differentdisplay areas and different display quality. For example, higherresolution images may be displayed on one of the display portions 9631 aand 9631 b.

FIG. 12B illustrates the tablet terminal which is folded. The tabletterminal in this embodiment includes the housing 9630, a solar cell9633, a charge and discharge control circuit 9634, a battery 9635, and aDCDC converter 9636. In FIG. 12B, a structure including the battery 9635and the DCDC converter 9636 is illustrated as an example of the chargeand discharge control circuit 9634.

Since the tablet terminal is foldable, the housing 9630 can be closedwhen the tablet terminal is not in use. As a result, the display portion9631 a and the display portion 9631 b can be protected, therebyproviding a tablet terminal with high endurance and high reliability forlong-term use.

The tablet terminal illustrated in FIGS. 12A and 12B can have otherfunctions such as a function of displaying various kinds of data (e.g.,a still image, a moving image, and a text image), a function ofdisplaying a calendar, a date, the time, or the like on the displayportion, a touch-input function of operating or editing the datadisplayed on the display portion by touch input, and a function ofcontrolling processing by various kinds of software (programs).

The solar cell 9633 provided on a surface of the tablet terminal cansupply power to the touchscreen, the display portion, a video signalprocessing portion, or the like. Note that a structure in which thesolar cell 9633 is provided on one or both surfaces of the housing 9630is preferable because the battery 9635 can be charged efficiently.

The structure and operation of the charge and discharge control circuit9634 illustrated in FIG. 12B are described with reference to a blockdiagram of FIG. 12C. FIG. 12C illustrates the solar cell 9633, thebattery 9635, the DCDC converter 9636, a converter 9638, switches SW1 toSW3, and a display portion 9631. The battery 9635, the DCDC converter9636, the converter 9638, and the switches SW1 to SW3 correspond to thecharge and discharge control circuit 9634 illustrated in FIG. 12B.

First, description is made on an example of the operation in the casewhere power is generated by the solar cell 9633 with the use of externallight. The voltage of the power generated by the solar cell is raised orlowered by the DCDC converter 9636 so as to be voltage for charging thebattery 9635. Then, when power from the solar cell 9633 is used for theoperation of the display portion 9631, the switch SW1 is turned on andthe voltage of the power is raised or lowered by the converter 9638 soas to be voltage needed for the display portion 9631. When images arenot displayed on the display portion 9631, the switch SW1 is turned offand the switch SW2 is turned on so that the battery 9635 is charged.

Although the solar cell 9633 is described as an example of a powergeneration unit, the power generation unit is not particularly limited,and the battery 9635 may be charged by another power generation unitsuch as a piezoelectric element or a thermoelectric conversion element(Peltier element). The battery 9635 may be charged by a non-contactpower transmission module capable of performing charging by transmittingand receiving power wirelessly (without contact), or another charge unitused in combination, and the power generation unit is not necessarilyprovided.

Note that the organometallic complex of one embodiment of the presentinvention can be used for an organic thin-film solar cell. Specifically,the organometallic complex can be used in a carrier-transport layersince the organometallic complex has a carrier-transport property. Theorganometallic complex can be photoexcited and hence can be used in apower generation layer.

One embodiment of the present invention is not limited to the tabletterminal having the shape illustrated in FIGS. 12A to 12C as long as thedisplay portion 9631 is included.

FIGS. 13A to 13C illustrate a foldable portable information terminal9310. FIG. 13A illustrates the portable information terminal 9310 thatis opened. FIG. 13B illustrates the portable information terminal 9310that is being opened or being folded. FIG. 13C illustrates the portableinformation terminal 9310 that is folded. The portable informationterminal 9310 is highly portable when folded. When the portableinformation terminal 9310 is opened, a seamless large display region ishighly browsable.

A display panel 9311 is supported by three housings 9315 joined togetherby hinges 9313. Note that the display panel 9311 may be a touch panel(an input/output device) including a touch sensor (an input device). Bybending the display panel 9311 at a connection portion between twohousings 9315 with the use of the hinges 9313, the portable informationterminal 9310 can be reversibly changed in shape from an opened state toa folded state. The light-emitting device of one embodiment of thepresent invention can be used for the display panel 9311. A displayregion 9312 in the display panel 9311 is a display region that ispositioned at the side surface of the portable information terminal 9310that is folded. On the display region 9312, information icons, fileshortcuts of frequently used applications or programs, and the like canbe displayed, and confirmation of information and start of applicationcan be smoothly performed.

Example 1 Synthesis Example 1

In this synthesis example, a synthesis example of{2-[6-(3,5-dimethyl-pyrazol-1-yl-κN²)-1,2-phenylene-κC¹]oxy[10-(2-pyridinyl-κN)-phenothiazine-2,1-diyl-κC¹]}platinum(II)(abbreviation: [Pt(pptOppz)]), which is the organometallic complex ofone embodiment of the present invention and represented by thestructural formula (100) in Embodiment, is specifically described. Astructural formula of [Pt(pptOppz)] is shown below.

Step 1: Synthesis of 2-methoxy-10-(pyridin-2-yl)-phenothiazine

First, 3.1 g of 2-methoxy phenothiazine, 3.1 g of 2-iodopyridine, and2.0 g of sodium-t-butoxide were put into a three-neck flask equippedwith a reflux pipe, and the air in the flask was replaced with nitrogen.Then, 97 mL of toluene, 0.56 g of2-dicyclohexylphosphino-2′,6′-dimethoxybiphenyl (product name: SPhos),and 0.62 g of tris(dibenzylideneacetone)dipalladium(0) (abbreviation:Pd₂(dba)₃) were added to this mixture, and the mixture was heated andstirred at 130° C. for 14 hours. Water was added to the obtainedmixture, and an organic layer was extracted with ethyl acetate. Thesolution of the extract was washed with saturated brine. Then, magnesiumsulfate was added and filtration was performed. The solvent of thefiltrate was distilled off and the obtained residue was purified byflash column chromatography using ethyl acetate and hexane in a ratio of1:5 as a developing solvent, so that the desired substance was obtainedas 2.2 g of a brown oily substance in a yield of 52%. The synthesisscheme of the step 1 is illustrated in the following equation (1-1).

Step 2: Synthesis of 2-hydroxy-10-(pyridin-2-yl)-phenothiazine

Next, 7.1 g of 2-methoxy-10-(pyridin-2-yl)-phenothiazine and 13 g ofpyridine hydrochloride were put into a three-neck flask equipped with areflux pipe, and the air in the flask was replaced with nitrogen. Themixture was heated and stirred at 170° C. for 7 hours. Furthermore, 2 gof pyridine hydrochloride was added, and the mixture was heated andstirred at 170° C. for 6 hours. The temperature of the flask was reducedto 90° C., ethyl acetate and water were added, and the mixture wasstirred for 30 minutes. An organic layer of the obtained mixturesolution was extracted with ethyl acetate. The solution of the extractwas washed with saturated brine. Then, magnesium sulfate was added andfiltration was performed. The solvent of the filtrate was distilled off,a solution containing ethyl acetate and hexane in a ratio of 1:2 wasadded to the obtained residue, and filtration was performed. Thisresidue was dissolved in ethyl acetate, and the mixture was filteredthrough a filter aid filled with Celite (produced by Wako Pure ChemicalIndustries, Ltd., Catalog No. 531-16855). The solvent of the filtratewas distilled off and recrystallization was performed with toluene, sothat the desired substance was obtained as 3.0 g of a greenish graysolid in a yield of 45%. The synthesis scheme of the step 2 isillustrated in the following equation (1-2).

Step 3: Synthesis of 1-(3-iodophenyl)-3,5-dimethylpyrazol

Next, 5.0 g of 1,3-diiodobenzene, 1.6 g of 3,5-dimethylpyrazol, 220 mgof copper(I) oxide, 370 mg of pyridin-2-aldoxime, and 12 g of cesiumcarbonate were put into a three-neck flask equipped with a reflux pipe,and the air in the flask was replaced with nitrogen. Then, 300 mL ofacetonitrile was added, and the mixture was refluxed for 37 hours. Theobtained mixture was dissolved in dichloromethane, and the mixture wasfiltered through a filter aid filled with Celite. The solvent of thefiltrate was distilled off and purification was performed by silica gelcolumn chromatography using ethyl acetate and hexane in a ratio of 1:5as a developing solvent, so that the desired substance was obtained as3.0 g of a brown oily substance in a yield of 40%. The synthesis schemeof the step 3 is illustrated in the following equation (1-3).

Step 4: Synthesis of2-[3-(3,5-dimethylpyrazol-1-yl)phenoxy]-10-(pyridin-2-yl)-phenothiazine(abbreviation: HpptOppz)

Next, 1.0 g of 2-hydroxy-10-(pyridin-2-yl)-phenothiazine, 1.3 g of1-(3-iodophenyl)-3,5-dimethylpyrazol, 1.1 g of picolinic acid, and 3.6 gof potassium phosphate were put into a three-neck flask equipped with areflux pipe, and the air in the flask was replaced with nitrogen. Then,100 mL of dimethyl sulfoxide and 0.33 g of copper iodide were added, andthe mixture was heated at 150° C. for 14 hours. Furthermore, 1.1 g ofpicolinic acid, 3.6 g of potassium phosphate, and 0.33 g of copperiodide were added, and the mixture was heated at 150° C. for 15 hours.Water was added to the obtained mixture, and an organic layer wasextracted with ethyl acetate. The solution of the extract was washedwith saturated brine. Then, magnesium sulfate was added and filtrationwas performed. The solvent of the filtrate was distilled off and theobtained residue was purified by flash column chromatography using ethylacetate and hexane in a ratio of 1:5 as a developing solvent, so thatthe desired substance was obtained as 1.3 g of a yellow solid in a yieldof 82%. The synthesis scheme of the step 4 is illustrated in thefollowing equation (1-4).

Step 5: Synthesis of{2-[6-(3,5-dimethyl-pyrazol-1-yl-κN²)-1,2-phenylene-KC]oxy[10-(2-pyridinyl-κN)-phenothiazine-2,1-diyl-κC¹]}platinum(II)(abbreviation: [Pt(pptOppz)])>

Next, 1.3 g of HpptOppz, 1.3 g of potassium tetrachloroplatinate(II),and 40 mL of glacial acetic acid were added to the flask, the air in theflask was replaced with nitrogen, and the mixture was refluxed for 56hours. Water was added to the obtained mixture, and the mixture wasstirred for 20 minutes and filtered. This residue was purified byneutral silica gel column chromatography using dichloromethane andhexane in a ratio of 7:5 as a developing solvent. The solvent wasdistilled off from the obtained fraction of the desired substance andrecrystallization was performed with a mixed solvent of chloroform,dichloromethane, methanol, and hexane to give 0.42 g of a yellowishwhite solid in a yield of 21%. The synthesis scheme of the step 5 isillustrated in the following equation (1-5).

Analysis results by nuclear magnetic resonance (¹H-NMR) spectroscopy ofthe yellowish white solid obtained in the step 5 are described below.FIGS. 14A and 14B show the ¹H-NMR charts. These results revealed that[Pt(pptOppz)], which is the organometallic complex of one embodiment ofthe present invention, was obtained.

¹H-NMR. δ (CDCl₃): 2.23 (s, 3H), 2.69 (s, 3H), 6.12 (s, 1H), 6.90-6.99(m, 4H), 7.01-7.03 (t, 1H), 7.12-7.17 (m, 5H), 7.34-7.37 (t, 1H),7.64-7.67 (t, 1H), 8.83 (dd, 1H).

Next, an ultraviolet-visible absorption spectrum (hereinafter, simplyreferred to as an absorption spectrum) and an emission spectrum of adichloromethane solution of [Pt(pptOppz)] were measured. The measurementof the absorption spectrum was conducted at room temperature in such amanner that an ultraviolet-visible light spectrophotometer (V550 typemanufactured by JASCO Corporation) was used and the dichloromethanesolution (0.015 mmol/L) was put in a quartz cell. In addition, themeasurement of the emission spectrum was performed at room temperaturein such a manner that a fluorescence spectrophotometer (FS920manufactured by Hamamatsu Photonics K.K.) was used and the degasseddichloromethane solution (0.015 mmol/L) was put in a quartz cell. FIG.15 shows measurement results of the absorption spectrum and emissionspectrum. The horizontal axis represents wavelength and the verticalaxes represent absorption intensity and emission intensity. In FIG. 15,two solid lines are shown; a thin line represents the absorptionspectrum, and a thick line represents the emission spectrum. FIG. 15shows the absorption spectrum obtained in such a manner that themeasured absorption spectrum of only dichloromethane that was in aquartz cell was subtracted from the measured absorption spectrum of thedichloromethane solution (0.015 mmol/L) that was in a quartz cell.

As shown in FIG. 15, [Pt(pptOppz)], which is the organometallic complexof one embodiment of the present invention, has an emission peak at 566nm, and yellow emission was observed from the dichloromethane solution.

Next, an emission spectrum of [Pt(pptOppz)] at 77 K was measured. Themeasurement of the emission spectrum was performed in such a manner thatan absolute PL quantum yield measurement system (Quantaurus-QY C11347-01manufactured by Hamamatsu Photonics K.K.) was used and a degassed2-methyltetrahydrofuran solution (0.079 mmol/L) was put in a quartzcell. FIG. 16 shows measurement results of the emission spectrum. Thehorizontal axis represents wavelength, and the vertical axis representsemission intensity.

As shown in FIG. 16, [Pt(pptOppz)], which is the organometallic complexof one embodiment of the present invention, has an emission peak at 453nm. Blue light emission was observed from the 2-methyltetrahydrofuransolution.

The absorption at around 420 nm in the absorption spectrum of[Pt(pptOppz)] can be assigned to the triplet MLCT (metal-to-ligandcharge transfer) transition, meaning that phosphorescence is possible.

Example 2

In this example, a light-emitting element using the organometalliccomplex of one embodiment of the present invention which is described inEmbodiment is described. Structural formulae of organic compounds usedfor a light-emitting element 1 are shown below.

(Method for Manufacturing Light-Emitting Element 1)

First, a film of indium tin oxide containing silicon oxide (ITSO) wasformed over a glass substrate by a sputtering method, so that the firstelectrode 101 was formed. The thickness of the first electrode 101 wasset to 70 nm and the area of the electrode was set to 2 mm×2 mm.

Next, in pretreatment for forming the light-emitting element over thesubstrate, a surface of the substrate was washed with water and baked at200° C. for 1 hour, and then UV ozone treatment was performed for 370seconds.

Then, the substrate was transferred into a vacuum evaporation apparatuswhose pressure was reduced to approximately 10⁻⁴ Pa, vacuum baking at170° C. for 30 minutes was performed in a heating chamber of the vacuumevaporation apparatus, and then the substrate was cooled down forapproximately 30 minutes.

Then, the substrate over which the first electrode 101 was formed wasfixed to a substrate holder provided in the vacuum evaporation apparatusso that the surface on which the first electrode 101 was formed faceddownward. Over the first electrode 101,4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation:DBT3P-II) represented by the structural formula (i) above andmolybdenum(VI) oxide were deposited to a thickness of 15 nm by aco-evaporation method using resistance heating so that the weight ratiowas 2:1 (=DBT3P-II: molybdenum oxide), whereby the hole-injection layer111 was formed.

Next, 4,4′-bis(9-carbazole)-2,2′-dimethylbiphenyl (abbreviation: dmCBP)represented by the above structural formula (ii) was deposited byevaporation to a thickness of 20 nm over the hole-injection layer 111 toform the hole-transport layer 112.

Then, 5,12-bis[3-(9H-carbazol-9-yl)phenyl]-5,12-dihydro-indolo[3,2-a]carbazole (abbreviation: mCzP2ICz) represented by the above structuralformula (iii), 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine(abbreviation: 35DCzPPy) represented by the above structural formula(iv), and{2-[6-(3,5-dimethyl-pyrazol-1-yl-κN²)-1,2-phenylene-κC¹]oxy[10-(2-pyridinyl-κN)-phenothiazine-2,1-diyl-κC¹]}platinum(II)(abbreviation: [Pt(pptOppz)]) represented by the above structuralformula (100) were deposited by co-evaporation to a thickness of 30 nmso that mCzP2ICz: 35DCzPPy: [Pt(pptOppz)]=0.5:0.5:0.05 (weight ratio),and then, 35DCzPPy and [Pt(pptOppz)] were deposited by co-evaporation toa thickness of 10 nm so that 35DCzPPy: [Pt(pptOppz)]=1:0.05 (weightratio), whereby the light-emitting layer 113 was formed.

Then, over the light-emitting layer 113, a film of 35DCzPPy was formedto a thickness of 10 nm by evaporation, and a film ofbathophenanthroline (abbreviation: BPhen) represented by the structuralformula (v) was formed to a thickness of 15 nm by evaporation to formthe electron-transport layer 114.

After the formation of the electron-transport layer 114, lithiumfluoride (LiF) was deposited by evaporation to a thickness of 1 nm toform the electron-injection layer 115. Then, aluminum was deposited byevaporation to a thickness of 200 nm to form the second electrode 102.Through the above-described steps, the light-emitting element 1 of thisexample was fabricated.

The element structure of the light-emitting element 1 is shown in atable below.

TABLE 1 Hole- Hole- Light- Electron- Electron- injection transportemitting transport injection layer layer layer layer layer 15 nm 20 nm30 nm 10 nm 10 nm 15 nm 1 mm DBT3P-II: dmCBP mCzP2ICz: 35DCzPPy:35DCzPPy BPhen LiF MoOx 35DCzPPy: [Pt(pptOppz)] (2:1) [Pt(pptOppz)](1:0.05) (0.5:0.5:0.05)

The light-emitting element 1 was sealed using a glass substrate in aglove box containing a nitrogen atmosphere so as not to be exposed tothe air (specifically, a sealing material was applied to surround theelement and UV treatment and heat treatment at 80° C. for 1 hour wereperformed at the time of sealing). Then, the initial characteristics andreliability of the light-emitting element were measured. Note that themeasurement was carried out in an atmosphere kept at 25° C.

FIG. 17 shows current density-luminance characteristics of thelight-emitting element 1. FIG. 18 shows luminance-current efficiencycharacteristics of the light-emitting element 1. FIG. 19 showsvoltage-luminance characteristics of the light-emitting element 1. FIG.20 shows voltage-current characteristics of the light-emitting element1. FIG. 21 shows luminance-external quantum efficiency characteristicsof the light-emitting element 1. FIG. 22 shows an emission spectrum ofthe light-emitting element 1.

FIGS. 17 to 22 reveal that the light-emitting element 1 emits greenlight and has high emission efficiency.

This application is based on Japanese Patent Application serial No.2015-091000 filed with Japan Patent Office on Apr. 28, 2015, the entirecontents of which are hereby incorporated by reference.

1. An organometallic complex represented by a general formula (G1),

wherein each of R¹ to R¹³ independently represents any of hydrogen, asubstituted or unsubstituted alkyl group having 1 to 6 carbon atoms, anda substituted or unsubstituted phenyl group, wherein A represents afive-membered heteroaromatic skeleton comprising two or three nitrogenatoms, and wherein Q represents an oxygen atom.
 2. An organometalliccomplex represented by a general formula (G2),

wherein each of R¹ to R¹³ independently represents any of hydrogen, asubstituted or unsubstituted alkyl group having 1 to 6 carbon atoms, anda substituted or unsubstituted phenyl group, wherein each of X¹, Y¹, andZ¹ independently represents a nitrogen atom or a carbon atom, whereinnone or one of X¹, Y¹, and Z¹ represents a nitrogen atom, wherein two orthree of X¹, Y¹, and Z¹ each represent a carbon atom, wherein the carbonatom may have a substituent or no substituent, and wherein Q representsan oxygen atom.
 3. An organometallic complex represented by a generalformula (G3),

wherein each of R¹ to R¹³ and R²⁰ independently represents any ofhydrogen, a substituted or unsubstituted alkyl group having 1 to 6carbon atoms, and a substituted or unsubstituted phenyl group, whereineach of X² and Z² independently represents a nitrogen atom or a carbonatom, wherein, when one of X² and Z² represents a nitrogen atom, theother of X² and Z² represents a carbon atom, wherein, when one or bothof X² and Z² represent a carbon atom, the carbon atom may have asubstituent or no substituent, and wherein Q represents an oxygen atom.4. An organometallic complex represented by a general formula (G4),

wherein each of R¹ to R¹³ and R²¹ independently represents any ofhydrogen, a substituted or unsubstituted alkyl group having 1 to 6carbon atoms, and a substituted or unsubstituted phenyl group, whereineach of Y³ and Z³ independently represents a nitrogen atom or a carbonatom, wherein, when one of Y³ and Z³ represents a nitrogen atom, theother of Y³ and Z³ represents a carbon atom, wherein, when one or bothof Y³ and Z³ represent a carbon atom, the carbon atom may have asubstituent or no substituent, and wherein Q represents an oxygen atom.5. An organometallic complex represented by a general formula (G5),

wherein each of R¹ to R¹³ and R²² independently represents any ofhydrogen, a substituted or unsubstituted alkyl group having 1 to 6carbon atoms, and a substituted or unsubstituted phenyl group, whereineach of X⁴ and Y⁴ independently represents a nitrogen atom or a carbonatom, wherein, when one of X⁴ and Y⁴ represents a nitrogen atom, theother of X⁴ and Y⁴ represents a carbon atom, wherein, when one or bothof X⁴ and Y⁴ represent a carbon atom, the carbon atom may have asubstituent or no substituent, and wherein Q represents an oxygen atom.6. An organometallic complex represented by a general formula (G6),

wherein each of R¹ to R¹³ and R³⁰ to R³² independently represents any ofhydrogen, a substituted or unsubstituted alkyl group having 1 to 6carbon atoms, and a substituted or unsubstituted phenyl group, andwherein Q represents an oxygen atom.
 7. The organometallic complexaccording to claim 6, wherein each of R³⁰ and R³² represents asubstituted or unsubstituted alkyl group.
 8. The organometallic complexaccording to claim 6, wherein R³¹ represents a substituted orunsubstituted alkyl group or a substituted or unsubstituted phenylgroup.
 9. The organometallic complex according to claim 1, wherein R³represents a substituted or unsubstituted alkyl group or a substitutedor unsubstituted phenyl group.
 10. The organometallic complex accordingto claim 9, wherein R³ represents a t-butyl group or a phenyl group.11-16. (canceled)
 17. The organometallic complex according to claim 2,wherein R³ represents a substituted or unsubstituted alkyl group or asubstituted or unsubstituted phenyl group.
 18. The organometalliccomplex according to claim 17, wherein R³ represents a t-butyl group ora phenyl group.
 19. The organometallic complex according to claim 3,wherein R³ represents a substituted or unsubstituted alkyl group or asubstituted or unsubstituted phenyl group.
 20. The organometalliccomplex according to claim 19, wherein R³ represents a t-butyl group ora phenyl group.
 21. The organometallic complex according to claim 4,wherein R³ represents a substituted or unsubstituted alkyl group or asubstituted or unsubstituted phenyl group.
 22. The organometalliccomplex according to claim 21, wherein R³ represents a t-butyl group ora phenyl group.
 23. The organometallic complex according to claim 5,wherein R³ represents a substituted or unsubstituted alkyl group or asubstituted or unsubstituted phenyl group.
 24. The organometalliccomplex according to claim 23, wherein R³ represents a t-butyl group ora phenyl group.
 25. The organometallic complex according to claim 6,wherein R³ represents a substituted or unsubstituted alkyl group or asubstituted or unsubstituted phenyl group.
 26. The organometalliccomplex according to claim 25, wherein R³ represents a t-butyl group ora phenyl group.